Can't find focus with 3x Barlow...

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fatboy1271
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Can't find focus with 3x Barlow...

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Post by fatboy1271 »


Hey All,

I disappeared again... So frustrating, as I had just been getting my new equipment dialed in. Anyway, my daughter is now 16 months old and growing like crazy :) Hopefully now that she sleeps pretty much through the night I can start to get back out again.

With that said, I did get out for Jupiter at opposition and then last night for Saturn. I can get both planets in focus using my ES ED80 with my ASI120MC. Once I put on my 3x Barlow I cannot get focus. I tried everything I could think of for about 2 hours last night and finally gave up.

Should I need to remove focus extension tubes? I've used it several times over the years, including with this same setup, so maybe I'm just so out of practice that I made it more difficult then I needed to.

Hope everyone's safe!
fat
OTAs: Explore Scientific ED80 Essential Edition / The Little Guy (Celestron 90SLT)
Mount: Celestron Advanced VX
Gear: Canon 70D / Hutech LPS-D1-48 / ES 2" Field Flattener / QHY PoleMaster / Celestron GPS / ZWO ASI120MC / Orion 50mm Guide Scope / ZWO EAF
Software: CPWI / PHD2 / N.I.N.A / Stellarium/StellariumScope/Remote Control / PI / RegiStax 6 / AutoStakkert!2 / PIPP | Retired? BackyardEOS Premium
EPs: Stock Celestron 9mm and 24mm / Celestron Omni 32mm (I love this one!) / Celestron X-Cel LX 3x Barlow (I think 2X would have been smarter...)
Support Staff (Loved Ones!): CeCe, Ro, and Geno
Let's Go Pens!!!
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Ozypic
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Re: Can't find focus with 3x Barlow...

#2

Post by Ozypic »


Hi there Fatboy, haha that sounds wrong.. Hi there not so skinny... hmmm no better...
Hi there ...
I have a 2x and a 3x barlow. I bought the 3x to use as an extension tube to go with the 2x . Both barlows have removable lenses in them.
If I dont use the 3x for the planets they are just to small in the pic...
Anyways..... If I want 3x I take the lens out of the 2x and it becomes the extension tube. The important thing for my set up is the camera has to go into the barlow with the lense and it then goes in the tube without the lense ,then it goes into the telescope.... I'm using an f5 refractor and the same camera as you...
Once I find the planet . I use the Barthinov mask ,whack the gain up to maximum and the exposure up a bit ( to get it bright) so I can get the thing focused....
I'm the same, the gear only comes out now and then and I have to learn all over each time ....
Best of luck, Phill
Phill. Dreaming of Clear Skys .... :D :D :D
SCOPE : Skywatcher 120X600 ST Achromatic Refractor. 
EP's : 25mm & 10mm Plossl , Celestron 8/24mm Zoom EP,
Filters : Solar filter, Badder Fringe Killer & Moon/Skyglow. 
MOUNT : Skywatcher Star Discovery goto Mount.
CAMERAS : ZWO 120 asi MC. / Sony HX400V 50X Zoom.
Binoculars : Saxon 10x50
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sdbodin United States of America
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Re: Can't find focus with 3x Barlow...

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Post by sdbodin »


fatboy1271 wrote: Tue Jul 21, 2020 9:54 pm Hey All,


Should I need to remove focus extension tubes?
Hope everyone's safe!
fat
YES, yes, a barlow works because it intercepts the converging cone of light before it gets to focus. Sounds like it was never inside of the primary focal plane. Total movement of any barlow is from at the focal plane, magnification is then zero, to one focal length of the barlow inside focal plane, then magnification is infinity.

Ref, Sam Brown, "All About Telescopes"

Steve
Scopes; Meade 16 LX200, AT80LE, plus bunch just sitting around gathering dust
Cameras; Atik 460ex mono, Zwo ASI1600MC-cool, QHY5L-II color and mono
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JayTee United States of America
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Re: Can't find focus with 3x Barlow...

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Post by JayTee »


Hi and welcome back.

I'm going to take the contrary position and I may be totally wrong, but here's my reasoning. Remember how we tell Newtonian owners who are trying to get an in-focus image with their DSLR and it just doesn't work because they can't get the sensor close enough to the mirror. So we tell them to insert a barlow to lengthen the FL to get an in-focus image on the DSLR. So if you are adding a 3X barlow, you may not have enough extension tubes.

Just me thinking out loud and it could be wrong and I'm too lazy to go out to my ES 80, throw in a barlow, and see what happens.

Cheers,
JT
∞ 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°

Searching the skies since 1966. "I never met a scope I didn't want to keep."

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fatboy1271
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Re: Can't find focus with 3x Barlow...

#5

Post by fatboy1271 »


Thanks [mention]Ozypic[/mention], [mention]sdbodin[/mention], and [mention]JayTee[/mention]! I'll give it another go, but probably not tonight. The wife complains I'm too tired when I'm outside all night and don't get enough sleep... Pfft, whatever :)
OTAs: Explore Scientific ED80 Essential Edition / The Little Guy (Celestron 90SLT)
Mount: Celestron Advanced VX
Gear: Canon 70D / Hutech LPS-D1-48 / ES 2" Field Flattener / QHY PoleMaster / Celestron GPS / ZWO ASI120MC / Orion 50mm Guide Scope / ZWO EAF
Software: CPWI / PHD2 / N.I.N.A / Stellarium/StellariumScope/Remote Control / PI / RegiStax 6 / AutoStakkert!2 / PIPP | Retired? BackyardEOS Premium
EPs: Stock Celestron 9mm and 24mm / Celestron Omni 32mm (I love this one!) / Celestron X-Cel LX 3x Barlow (I think 2X would have been smarter...)
Support Staff (Loved Ones!): CeCe, Ro, and Geno
Let's Go Pens!!!
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