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Portable OTA for astrophotography

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#1 mr1337

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Posted 28 June 2020 - 10:07 PM

Looking at finding a more portable solution for astrophotography and have been looking at the RedCat, GT-81, AstroTech 80EDT, Televue 85, SVX80T, SW 80 Esprit... RedCat is a bit of an outlier but was nice because it was the lightest option to be paired up with my SkyGuider Pro, but also looking to have an alternative to the 1422mm focal length of the EdgeHD8 on my primary mount (or maybe piggyback. Under $2k is an ideal target, else I'd be looking at something like a Baby-Q. 

 

Any recommendations or things I forgot to put into the consideration set? 

 

Thanks!

MR

 

 



#2 Hesiod

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Posted 29 June 2020 - 12:35 AM

With the SGP my first choice would be a 200-ish lens, as fast as can find (if have Canon their ef200l 2.8 is quite nice and not overly expensive).
If want a "telescope", beside the RedCat I would suggest the Vixen FL55ss (which was the one I chose, truly excellent), the Tak FS60 (IMHO has a worse focuser and its reducer is a bit outdated) or the Borg 55.
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#3 bobzeq25

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Posted 29 June 2020 - 01:08 AM

I'd drop the longer heavier scopes off your list with that mount.

 

Camera lenses are good.  So is the Redcat.  The AT60ED is another possibility.

 

I like my Stellarvue SV70T, but availability from Stellarview is very restricted.  You can find them used.  Likewise used William Optics 71s (discontinued) with integrated flattener can be found.  This TS scope appears to be similar, I like my TS130 F7.

 

https://www.teleskop...-Objective.html

 

Meade has a quad 70.  I have no good information about quality.


Edited by bobzeq25, 29 June 2020 - 01:08 AM.

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#4 mr1337

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Posted Yesterday, 01:19 AM

Thanks for the recommendations! Ended up finding a good deal on a meade 70mm quad apo... just tried it out for the first time and it seemed like focus was right at the most racked-in position. Since that scope's backfocus is at 55mm I had an adjustible spacer set to 42.5mm (since camera backfocus is 12.5mm) but just shortened it a bit so I could get things into focus.

 

Should I be racking out the focuser a bit so I can have some forward/backward play? My frame of reference is the crayford on my SCT where I set the crayford to about midway (which gets the camera plane to the 105mm critical focus distance for the ota) and then adjust the primary focus to get things tight before tightening the mirror locks.



#5 bobzeq25

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Posted Yesterday, 02:37 PM

Thanks for the recommendations! Ended up finding a good deal on a meade 70mm quad apo... just tried it out for the first time and it seemed like focus was right at the most racked-in position. Since that scope's backfocus is at 55mm I had an adjustible spacer set to 42.5mm (since camera backfocus is 12.5mm) but just shortened it a bit so I could get things into focus.

 

Should I be racking out the focuser a bit so I can have some forward/backward play? My frame of reference is the crayford on my SCT where I set the crayford to about midway (which gets the camera plane to the 105mm critical focus distance for the ota) and then adjust the primary focus to get things tight before tightening the mirror locks.

I like having the focuser toward the middle of its travel.  And a good focuser will be more stable than the thin walled spacers, so reducing the length of those is a (small) positive.




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