Not quite: "Here is one way that lets you use the laser to get the accuracy of a Cheshire, as well as its insensitivity to centering errors." (From the "Special situations"-page, under "A Barlowed Laser Collimator".)Lady Fraktor wrote: ↑Wed Aug 12, 2020 4:23 am Perhaps starting out you may want to learn the collimation cap and cheshire methods before trying using a barlowed collimator.
Squaring the secondary under the focuser first is essential to aligning the primary, the method linked by Henk is a good one as well but adds a step that may not be required.
What makes the method insensitive to other collimation errors except primary mirror?
When Nils Olof Carlin mentions this he means using a Cheshire not the laser.
Reading some of your questions/ comments it seems you are possibly reading to far down the page and combining Schmidt and spherical mirrors.
Barlowed laser collimation by Nils Olof Carlin?
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Re: Barlowed laser collimation by Nils Olof Carlin?
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Re: Barlowed laser collimation by Nils Olof Carlin?
I _think_ I got the primary mirror set using the collimated laser method. Now I'm going through other phases as I get to know what the heck I'm doing. But easy does it. And at the end I'll probably know whether or not the collimated laser method works the way I think it works. It looks like the tube has been in parts and was quickly put together when I bought it. I think I was right to suspect everything.
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Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
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Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
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Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
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Re: Barlowed laser collimation by Nils Olof Carlin?
Gary's article is splendid in the way he explains what it all comes down to. For any Newt there are an infinite number of ways of doing a correct collimation each with a different result, caused by the 4 degrees of freedom in the positioning of the secondary (6 DOF minus 2 for placing the laser in the donut). The collimation of the primary follows from it and does not add or remove degrees of freedom. The confusion in a lot of articles on collimation is about these 4 degrees of freedom. As Gary points out, none of this matters much when doing a reasonable job at squaring the secondary - the differences between each possible correct collimation is just a slight change in the illumination of the focal plane. What really matters is that the eyepiece is aimed at the center of the primary, and the primary is aimed at the eyepiece.Lady Fraktor wrote: ↑Wed Aug 12, 2020 4:23 am Squaring the secondary under the focuser first is essential to aligning the primary, the method linked by Henk is a good one as well but adds a step that may not be required.
While at first I did not like his method because he starts with the primary and has to redo it in the end, the upside is that he does it all with just a collimation cap. And really after collimating the secondary once you probably never need to do it again, and a collimation cap is perfect for collimating the primary.
Well except that personally I hate going back and forth from the rear to the eyepiece and really enjoy watching the laser reflection fall into place while turning the screws from the rear. And unless your laser collimator and/or spider vanes are flopping around, Barlowing does not add accuracy. And if the spider vanes are flopping around you have a bigger problem that needs to be fixed first. Your time and money is better spent getting a quality laser collimator that fits well than Barlowing it IMHO. My Howie Glatter plus tublug does both.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
This is why I constantly tell beginners to stay away from lasers when starting and learn to do it with a collimation cap and Cheshire.SkyHiker wrote: ↑Wed Aug 12, 2020 11:14 pm While at first I did not like his method because he starts with the primary and has to redo it in the end, the upside is that he does it all with just a collimation cap. And really after collimating the secondary once you probably never need to do it again, and a collimation cap is perfect for collimating the primary.
Once set up a collimation cap is the simplest and most powerful tool available.
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Re: Barlowed laser collimation by Nils Olof Carlin?
I think the laser beats the Cheshire in collimating the secondary because it uses a path length equal to the entire focal length (to the donut) to place the optical axis while with the Cheshire the path is from the eyepiece to the cross hairs only a few inches away. The cross hairs are fuzzy, which makes it even harder - and how accurately were they placed in the factory? Impossible to get much accuracy out of that IMHO. Plus, the convenience of not having to walk back and forth while collimating the primary with a laser should appeal to all beginners and make it more pleasant. In time they will learn how to work around some minor flaws.Lady Fraktor wrote: ↑Wed Aug 12, 2020 11:25 pmThis is why I constantly tell beginners to stay away from lasers when starting and learn to do it with a collimation cap and Cheshire.SkyHiker wrote: ↑Wed Aug 12, 2020 11:14 pm While at first I did not like his method because he starts with the primary and has to redo it in the end, the upside is that he does it all with just a collimation cap. And really after collimating the secondary once you probably never need to do it again, and a collimation cap is perfect for collimating the primary.
Once set up a collimation cap is the simplest and most powerful tool available.
I like that it is battery-less though. And for cases where the laser misses the secondary on the way back you need a Cheshire.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
I've been checking the tube, and pretty much everything is out of alignment. I think I'm going to get a Chesire and collimation cap, and do a complete setup, so that later on, collimation is easier. The sky is still too bright to find anything interesting, so I have the time. And now it's good time to learn the basics of collimation. The job feels hard when you can't trust any component in pretty much any any respect. In most cases people can trust that at least the focuser is square and the secondary mirror placement is right. In my tube the secondary mirror is about 5 mm too low, and it didn't look round.
About the barlowed laser, I found a nice description here: http://www.collimator.com/collimation
It explains roughly how the method works (under heading "BARLOWED LASER PRIMARY ADJUSTMENT").
It works backwards compared to star collimation. The barlowed laser is a point source of light for the primary mirror's point of view.
I think the thought model in collimation in general is that focuser has its optical axis and so does the primary. They are aligned to be the same, as if there was no secondary mirror. The secondary mirror is just thought to deflect those axes "mechanically". Of course the secondary mirror needs to be aligned too, but as a flat thing, it doesn't have an optical axis to align.
About the barlowed laser, I found a nice description here: http://www.collimator.com/collimation
It explains roughly how the method works (under heading "BARLOWED LASER PRIMARY ADJUSTMENT").
It works backwards compared to star collimation. The barlowed laser is a point source of light for the primary mirror's point of view.
I think the thought model in collimation in general is that focuser has its optical axis and so does the primary. They are aligned to be the same, as if there was no secondary mirror. The secondary mirror is just thought to deflect those axes "mechanically". Of course the secondary mirror needs to be aligned too, but as a flat thing, it doesn't have an optical axis to align.
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Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
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Some filters (#80A, ND-96, ND-09, Astronomik UHC)
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Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
Don't make it harder than it is. The laser will do just fine.
Collimate the laser if needed. This is a one time chore.
Square the secondary. Loosen everything, slide it, turn it, tilt it, just to get a feeling for it. It can all be fixed don't worry.
Once familiar, set it at roughly 45 degrees so you can see the primary in it and it looks about round and centered. Tighten all screws.
Get the laser in the donut using the hex screws.
Get the laser in the bulls eye.
You are done. It's that easy.
Explore the Barlowed laser later on once you get the drill. It is nice but not essential for good collimation if the secondary collimation is stable.
Collimate the laser if needed. This is a one time chore.
Square the secondary. Loosen everything, slide it, turn it, tilt it, just to get a feeling for it. It can all be fixed don't worry.
Once familiar, set it at roughly 45 degrees so you can see the primary in it and it looks about round and centered. Tighten all screws.
Get the laser in the donut using the hex screws.
Get the laser in the bulls eye.
You are done. It's that easy.
Explore the Barlowed laser later on once you get the drill. It is nice but not essential for good collimation if the secondary collimation is stable.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
I did it once in the beginning, but started to question. And a while ago I found out that the secondary mirror was not fine. When I checked more carefully from the focuser tube. It was about 5 mm too low and about the same amount in the side. I could still make the laser hit the center of the primary mirror and back to the hole in the target of the laser.
Yesterday I actually took the secondary totally out with the spider, and looked and measured it. I think it'll be easier to keep it squared later. It's pretty hard to measure the secondary mirror's place, but it's easy to measure the secondary mirror holder's place and calculate the mirror's place from that.
Once I get the thing in shape, the laser is probably good enough for quick checks.
Yesterday I actually took the secondary totally out with the spider, and looked and measured it. I think it'll be easier to keep it squared later. It's pretty hard to measure the secondary mirror's place, but it's easy to measure the secondary mirror holder's place and calculate the mirror's place from that.
Once I get the thing in shape, the laser is probably good enough for quick checks.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
Measuring the secondary to understand where to position it does not work because of the effect of perspective. See the drawings in Don Pensack's article. The center of the secondary (from linear measurements) will not be the center as seen through the focuser at close distance, for instance. Trying to get it right by measuring is not only overcomplicating it but you will get it wrong. The right viewing distance is where the focal plane of the primary is at. This is also where the stop of an eyepiece is at when you have a star in focus.turboscrew wrote: ↑Thu Aug 13, 2020 12:06 pm I did it once in the beginning, but started to question. And a while ago I found out that the secondary mirror was not fine. When I checked more carefully from the focuser tube. It was about 5 mm too low and about the same amount in the side. I could still make the laser hit the center of the primary mirror and back to the hole in the target of the laser.
Yesterday I actually took the secondary totally out with the spider, and looked and measured it. I think it'll be easier to keep it squared later. It's pretty hard to measure the secondary mirror's place, but it's easy to measure the secondary mirror holder's place and calculate the mirror's place from that.
Once I get the thing in shape, the laser is probably good enough for quick checks.
Make sure that the 3 hex screws of the secondary are in the neutral position so the angle is about 45 degrees. They should all be about equally deep turned in. This is important otherwise it will look elliptical or it will be tilted around the axis, which is not good for using the screws to tilt the mirror once the secondary is in place.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
I understand that the geometrical center of the secondary mirror is not the optical center. And when I looked into the tube through the focuser, the secondary mirror didn't look round and there was a gap above it while the lower end of the secondary mirror was too low to see. Can it really be that the secondary mirror should be 4.75 mm closer to the back than the focuser? From "offset=minor axis/(4*focal ratio)" I got that. The minor axis is 75 mm and focal ratio is 4 (the major axis is 106 mm). I thought the offset were usually somewhere between 1 mm and 2 mm. I also wonder if the downward offset is the same as the backward offset?SkyHiker wrote: ↑Thu Aug 13, 2020 1:59 pmMeasuring the secondary to understand where to position it does not work because of the effect of perspective. See the drawings in Don Pensack's article. The center of the secondary (from linear measurements) will not be the center as seen through the focuser at close distance, for instance. Trying to get it right by measuring is not only overcomplicating it but you will get it wrong. The right viewing distance is where the focal plane of the primary is at. This is also where the stop of an eyepiece is at when you have a star in focus.turboscrew wrote: ↑Thu Aug 13, 2020 12:06 pm I did it once in the beginning, but started to question. And a while ago I found out that the secondary mirror was not fine. When I checked more carefully from the focuser tube. It was about 5 mm too low and about the same amount in the side. I could still make the laser hit the center of the primary mirror and back to the hole in the target of the laser.
Yesterday I actually took the secondary totally out with the spider, and looked and measured it. I think it'll be easier to keep it squared later. It's pretty hard to measure the secondary mirror's place, but it's easy to measure the secondary mirror holder's place and calculate the mirror's place from that.
Once I get the thing in shape, the laser is probably good enough for quick checks.
Make sure that the 3 hex screws of the secondary are in the neutral position so the angle is about 45 degrees. They should all be about equally deep turned in. This is important otherwise it will look elliptical or it will be tilted around the axis, which is not good for using the screws to tilt the mirror once the secondary is in place.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
The reason I wanted to measure, was to see if the offsets are taken into account in the way the mirror is attached to the holder. That is: if the middle of the holder is in the center of the tube, does the mirror have right "front - back offset".
Last edited by turboscrew on Thu Aug 13, 2020 3:07 pm, edited 1 time in total.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
You are aware that the optical axis is generally not the mechanical axis because most Newts are made with secondaries that have no offset, right? See Don Pensack's article. This could easily be several mm at the secondary. Does your math take that into account? If you don't trust your math (and I certainly don't but if you have a link I would like to check) you are better off doing it visually like everyone else does, and like the experts tell to do it.turboscrew wrote: ↑Thu Aug 13, 2020 2:22 pm I understand that the geometrical center of the secondary mirror is not the optical center. And when I looked into the tube through the focuser, the secondary mirror didn't look round and there was a gap above it while the lower end of the secondary mirror was too low to see. Can it really be that the secondary mirror should be 4.75 mm closer to the back than the focuser? From "offset=minor axis/(4*focal ratio)" I got that. The minor axis is 75 mm and focal ratio is 4 (the major axis is 106 mm). I thought the offset were usually somewhere between 1 mm and 2 mm. I also wonder if the downward offset is the same as the backward offset?
If you look at it from the right distance and it is elliptical, check the positions of the hex screws, and the mirror angle. Get it roughly to 45 degrees and at some point it will look round enough after trying a few times.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
"See Don Pensack's article". Which article?SkyHiker wrote: ↑Thu Aug 13, 2020 3:03 pmYou are aware that the optical axis is generally not the mechanical axis because most Newts are made with secondaries that have no offset, right? See Don Pensack's article. This could easily be several mm at the secondary. Does your math take that into account? If you don't trust your math (and I certainly don't but if you have a link I would like to check) you are better off doing it visually like everyone else does, and like the experts tell to do it.turboscrew wrote: ↑Thu Aug 13, 2020 2:22 pm I understand that the geometrical center of the secondary mirror is not the optical center. And when I looked into the tube through the focuser, the secondary mirror didn't look round and there was a gap above it while the lower end of the secondary mirror was too low to see. Can it really be that the secondary mirror should be 4.75 mm closer to the back than the focuser? From "offset=minor axis/(4*focal ratio)" I got that. The minor axis is 75 mm and focal ratio is 4 (the major axis is 106 mm). I thought the offset were usually somewhere between 1 mm and 2 mm. I also wonder if the downward offset is the same as the backward offset?
If you look at it from the right distance and it is elliptical, check the positions of the hex screws, and the mirror angle. Get it roughly to 45 degrees and at some point it will look round enough after trying a few times.
And I do trust my math. Went through technical university, and that's hard without math.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
I think we may be talking about the same thing here. I think "...if the offsets are taken into account in the way the mirror is attached to the holder" = "...most Newts are made with secondaries that have no offset"?SkyHiker wrote: ↑Thu Aug 13, 2020 3:03 pmYou are aware that the optical axis is generally not the mechanical axis because most Newts are made with secondaries that have no offset, right? See Don Pensack's article. This could easily be several mm at the secondary. Does your math take that into account? If you don't trust your math (and I certainly don't but if you have a link I would like to check) you are better off doing it visually like everyone else does, and like the experts tell to do it.turboscrew wrote: ↑Thu Aug 13, 2020 2:22 pm I understand that the geometrical center of the secondary mirror is not the optical center. And when I looked into the tube through the focuser, the secondary mirror didn't look round and there was a gap above it while the lower end of the secondary mirror was too low to see. Can it really be that the secondary mirror should be 4.75 mm closer to the back than the focuser? From "offset=minor axis/(4*focal ratio)" I got that. The minor axis is 75 mm and focal ratio is 4 (the major axis is 106 mm). I thought the offset were usually somewhere between 1 mm and 2 mm. I also wonder if the downward offset is the same as the backward offset?
If you look at it from the right distance and it is elliptical, check the positions of the hex screws, and the mirror angle. Get it roughly to 45 degrees and at some point it will look round enough after trying a few times.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
The offset needs to be there one way or another, because the mirror intersects a cone.
Mr. Carlin has a good picture of that: http://w1.411.telia.com/~u41105032/kolli/Kolli_6.gif
Mr. Carlin has a good picture of that: http://w1.411.telia.com/~u41105032/kolli/Kolli_6.gif
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
I mentioned that reference a few times, and expect that if you can't find it you will let me know.
What do you know... searching for "Don Pensack colllimation" actually works! Wow, how come it did not work for you?
https://www.catseyecollimation.com/pensack.pdf
You may but I don't.turboscrew wrote: ↑Thu Aug 13, 2020 3:20 pm And I do trust my math. Went through technical university, and that's hard without math.
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
I recommend that you leave the whole thing alone for a week, get it out of your system, then take a fresh look at it again. Paralysis by analysis. Read Gary Seronik's article again where he describes how people easily get off in the deep end and how there's no point in it except for the die hard nerds who understand this thoroughly. That's where you are now (except you are just learning).
... Henk. Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: Barlowed laser collimation by Nils Olof Carlin?
Thanks. I found that, but I thought that it was a wrong, Catseye specific article.SkyHiker wrote: ↑Thu Aug 13, 2020 3:31 pmI mentioned that reference a few times, and expect that if you can't find it you will let me know.
What do you know... searching for "Don Pensack colllimation" actually works! Wow, how come it did not work for you?
https://www.catseyecollimation.com/pensack.pdfYou may but I don't.turboscrew wrote: ↑Thu Aug 13, 2020 3:20 pm And I do trust my math. Went through technical university, and that's hard without math.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
I'm not hurrying with this. And you are right, I'm doing about 60% of learning and 40% of getting a good base setting done.SkyHiker wrote: ↑Thu Aug 13, 2020 3:35 pm I recommend that you leave the whole thing alone for a week, get it out of your system, then take a fresh look at it again. Paralysis by analysis. Read Gary Seronik's article again where he describes how people easily get off in the deep end and how there's no point in it except for the die hard nerds who understand this thoroughly. That's where you are now (except you are just learning).
The later settings are easier if the base setting is good - or so I've heard.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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Re: Barlowed laser collimation by Nils Olof Carlin?
Hmm... In the Don Pensack's article it says:
1. Collimation cap (A simple peep-hole, though not good enough for scopes below f/10. I don’t recommend these except, perhaps, as a quick check to see if the optical elements are at least in gross alignment at the start).
2. Laser collimator (not useful unless perfectly collimated itself, possessed of a small beam diameter, and not accurate enough for primary mirror collimation unless used with a Barlow lens, but quite useful in the dark. Mfrs.: Glatter, FarPoint, etc.
- Juha
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
Senior Embedded SW Designer
Telescope: OrionOptics XV12, Mount: CEM120, Tri-pier 360 and alternative dobson mount.
Grab 'n go: Omegon AC 102/660 on AZ-3 mount
Eyepieces: 26 mm Omegon SWAN 70°, 15 mm TV Plössl, 12.5 mm Baader Morpheus, 10 mm TV Delos, 6 mm Baader Classic Ortho, 5 mm TV DeLite, 4 mm and 3 mm TV Radians
Cameras: ZWO ASI 294MM Pro, Omegon veLOX 178C
OAG: TS-Optics TSOAG09, ZWO EFW 7 x 36 mm, ZWO filter sets: LRGB and Ha/OIII/SII
Explore Scientific HR 2" coma corrector, Meade x3 1.25" Barlow, TV PowerMate 4x 2"
Some filters (#80A, ND-96, ND-09, Astronomik UHC)
Laptop: Acer Enduro Urban N3 semi-rugged, Windows 11
LAT 61° 28' 10.9" N, Bortle 5
I don't suffer from insanity. I'm enjoying every minute of it.
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