Achieving focus with ASI 290 Guide and Orion ST80

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chris_g United States of America
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Achieving focus with ASI 290 Guide and Orion ST80

#1

Post by chris_g »


Hello all,

I'm missing the optics somehow here folks and am hoping someone can explain why I would not be able to achieve focus with the ZWO ASI 290MM guide without having to use a diagonal. I mean it works fine with the Orion 60mm, why is the 80ST different? I was able to achieve focus using an Orion correct image 1.25 diagonal, the only 1.25" I have. It did not use that much tube travel either to do it, so I figured I would have to go further out to achieve focus without the diagonal than with since it adds optical length. Or do I have this backwards, and I would. That didn't matter though, I couldn't foucs going full inward or outward, I also used the extension tube that came with it to give it more backward travel, no idea what I'm doing wrong or why a diaganol would work. However, I do believe that the diagonal messed with guiding.

Any insight would be appreciated.

Clear Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
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JayTee United States of America
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#2

Post by JayTee »


It shouldn't. The back focus should not be a factor and if you can't get the image to focus going the other way, just use spacers.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

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chris_g United States of America
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#3

Post by chris_g »


JayTee wrote: Sun Dec 18, 2022 10:32 pm It shouldn't. The back focus should not be a factor and if you can't get the image to focus going the other way, just use spacers.
The tracking was consistently off by a few pixels in the same direction on each sub, guiding graph looked good. The diagonal is a correct image version so it would reverse and flip the image, drift right would be translated by PHD2 to drift left and up would be down. Or at least that's my thought process with the tracking. Probably have it all wrong, it calibrated fine. Something else comes to mind about that, the ST80 not being in close enough alignment with the C8 along the central axis would produce a similar error in guiding, the equivalent of inducing flexure. Or is that wrong too?

Below is a pic of about where the camera achieved focus with the diagonal that produced a good tracking graph with image shift. The next one is with a 20mm extension and the draw tube fully extended still no focus, more extension tubes? I've got one more, I'll try adding it next time out. But the optics isn't making sense to me. It just seems to far back and the camera should have achieved focus about 8.5 mm farther back from where it did with the diagonal, its working back focus distance is 8.5mm. Again, at least that is my thought process, is it wrong?
20221218_210221.jpg
20221218_211236.jpg
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
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JayTee United States of America
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#4

Post by JayTee »


chris_g wrote: Mon Dec 19, 2022 3:43 am The tracking was consistently off by a few pixels in the same direction on each subs guiding graph looked good. The diagonal is a correct image version so it would reverse and flip the image, drift right would be translated by PHD2 to drift left, and up would be down. Or at least that's my thought process with the tracking. Probably have it all wrong, it calibrated fine. Something else comes to mind about that, the ST80 not being in close enough alignment with the C8 along the central axis would produce a similar error in guiding, the equivalent of inducing flexure. Or is that wrong too?
First off, never image or guide through a diagonal if you can at all help it. Also, your guiding axis being off from your imaging axis induces what's called "cone error". A small cone error (<5°) is almost never noticeable. A larger cone error, say greater than 20-30° takes a lot of exposure time before you do notice it.

My ES 80mm APO needs 6" of spacers for the sensor to come into focus. It looks goofy as all get out. But hey, you do what it takes.
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

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bobharmony
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#5

Post by bobharmony »


For my ST-80 and Orion StarShoot autoguider, I use an extension tube in the drawtube to get the camera into focus. Not the best for stability and I have tried to figure out how to support the entire train without success so far.

Bob
Hardware: Celestron C6-N w/ Advanced GTmount, Baader MK iii CC, Orion ST-80, Canon 60D (unmodded), Nikon D5300 (modded), Orion SSAG
Software: BYE, APT, PHD2, DSS, PhotoShop CC 2020, StarTools, Cartes du Ciel, AstroTortilla

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chris_g United States of America
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#6

Post by chris_g »


JayTee wrote: Mon Dec 19, 2022 9:43 am
chris_g wrote: Mon Dec 19, 2022 3:43 am The tracking was consistently off by a few pixels in the same direction on each subs guiding graph looked good. The diagonal is a correct image version so it would reverse and flip the image, drift right would be translated by PHD2 to drift left, and up would be down. Or at least that's my thought process with the tracking. Probably have it all wrong, it calibrated fine. Something else comes to mind about that, the ST80 not being in close enough alignment with the C8 along the central axis would produce a similar error in guiding, the equivalent of inducing flexure. Or is that wrong too?
First off, never image or guide through a diagonal if you can at all help it. Also, your guiding axis being off from your imaging axis induces what's called "cone error". A small cone error (<5°) is almost never noticeable. A larger cone error, say greater than 20-30° takes a lot of exposure time before you do notice it.

My ES 80mm APO needs 6" of spacers for the sensor to come into focus. It looks goofy as all get out. But hey, you do what it takes.
Wow, okey dokey then, more extension tubes... I tried not guiding through the diagonal but when I couldn't get focus, I brought out it out with an 10mm EP. Got that to focus then dropped in the 290 and got that to focus. I was going to make sure I got some sort of data with the C8! Love the contrast! Looking forward to when I actually have something worthwhile to share with it.

As always, thanks the enlightenment.

Clears Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
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chris_g United States of America
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#7

Post by chris_g »


bobharmony wrote: Mon Dec 19, 2022 2:41 pm For my ST-80 and Orion StarShoot autoguider, I use an extension tube in the drawtube to get the camera into focus. Not the best for stability and I have tried to figure out how to support the entire train without success so far.

Bob
Mine will be used primarily for EAA; this is a good trial run for when I decide on what camera I want to use for that. I think I know why I need two tubes; the back focus is 8.5mm for the mini while others are 12.5, Shorter working distance requires longer extension tubes. Kind of counter intuitive but I think I understand the math. Thanks.

Clear Skies,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
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Re: Achieving focus with ASI 290 Guide and Orion ST80

#8

Post by chris_g »


Wow, I added another 20mm extension tube and barely managed to focus with the ST80. It's hanging out there on it's very edge, really should have another tube. I tried focusing the OAG but that was no go, at least for now. Now on to other issues with the C8, still related to guiding.

Clear Skys,
Chris
Image Cam: Canon 6D (Ha mod), 600D (Stock), SVBony SV405CC
Image OTA: EvoStar ED80, WO Z73, C8-A XLT
Mount: EQ6-R Pro Pier, AZ-EQ5 Pro Pier
Guide OTA: Orion 60mm, WO 32mm, ZWO OAG, SV501P
Guide Cam: ZWO 120mm, 290mm mini
EAA OTA: Orion ST80
EAA Cam: SVBony SV705C
EP: Baader Hyperion Modular Set
Filters: L-Pro Canon EOS C, L-eNhance, L-Pro, Optolong Ha 7mm, Optolong Oiii 6.5mm, Optolong Sii 6.5mm, ES H-Beta
Session Control: Mini PC/Win11 Pro, APT 4.1, PHD2 2.6.10
Processing: PixInsight, DSS 4.2.6, Adobe PS CC, Astronomy Tools Action Set, Star Spikes Pro
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