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coma corrector advice

crashtestdummy

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cs1cjc

cs1cjc

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I am sure that you will be very happy with the Paracorr II and it will last a lifetime.

However I am slightly saddened by the outcome. There are good alternatives to the Paracorr which costs £460, including the Altair Astro (aka Astro-Tech, GSO) at £85, but the Paracorr still dominates the market despite being so highly priced. Why? I simply do not understand it!

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crashtestdummy

crashtestdummy

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I think another thing that does it for some is the televue name and rep.for me that isnt a factor and ive shown as much in eyepiece threads.in general i wont pay for something i can get thats nearly as good but much cheaper hence why i have the explore scientific eps.they are nearly as good but in some cases less than half price.the paracorr for me looks like a stand out product so i have bitten the bullet.second reason-resale.it will still be worth £400 in a year if i dont need/want it :)

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jam1e1

jam1e1

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Agree with comments whilst I would certainly not recommend going out buying a full range of tv eps, the two items that stand out for me are the tv powermate and paracorr, to me certainly get value compared to competition. For eps you can get great value from Meade and explorer scientific to name a few

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crashtestdummy

crashtestdummy

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has anyone used the paracorr with a 2" es focal extender?im wanting to barlow the 14 and 9mm es 100 degree and have done some reading up and want to make sure the paracorr isnt too deep to seat in the focal extender or if i will need the paracorr when barlowing the 14 and 9mm

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russ.will

russ.will

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I suspected as much. In practice with a reasonable choice of eyepieces the GSO needs no adjustment...

Quite, I find that I use the ES82 18 & 30mm in it and the 1.25" EPs (8.8, 11, 14 & Focal Extender with any of those) don't really need it. I fitted the correct extension tube to suit both the 18 &30mm and so it's little hassle to drop it in the focuser like a Barlow, when I fancy some wide field viewing with the 2" EPs. I worried that the +/-10mm latitude seemed rather generous when I bought it, but it seems, to my eyes, to be true. I wasted a lot of time trying to find the sweet spot, but the spot is so wide, it's a non-issue.
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Andyj

Andyj

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Quite, I find that I use the ES82 18 & 30mm in it and the 1.25" EPs (8.8, 11, 14 & Focal Extender with any of those) don't really need it. I fitted the correct extension tube to suit both the 18 &30mm and so it's little hassle to drop it in the focuser like a Barlow, when I fancy some wide field viewing with the 2" EPs. I worried that the +/-10mm latitude seemed rather generous when I bought it, but it seems, to my eyes, to be true. I wasted a lot of time trying to find the sweet spot, but the spot is so wide, it's a non-issue.

This is interesting to know. I am expecting to need a coma corrector in future and was concerned I might have trouble with getting the adjustment right with different EPs. So was thinking I would have to play safe but expensive and go for the TV for that reason. It's good to hear that is not necessarily the case. Do you (or anyone) happen to know if the Revelation coma corrector sold by Telescope House is from the same stable as the Altair-Astro/GSO? It seems to look identical although they claim in the blurb that it doesn't change the focal length, which I take with a pinch of salt.

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cs1cjc

cs1cjc

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The Revelation name has been used in the past for GSO produced equipment and this looks identical to the GSO, so I am pretty sure that it is. Expect additional magnification of about 11%. You will want some additional spacing in the form of empty 2" filters or Hyperion fine tuning ring to get the back focus to around 75mm (+/-10mm) for your most used/ widest angle eyepieces. Let us know how you get on!

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Damo636

Damo636

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I'm going to buy the GSO for use with both my 100 degree eyepieces. Coma is only mildly offensive in these at f5, but thanks to this thread, curiosity has gotten the better of me and I want to see how much a CC cleans up the views :smiley:

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Bart

Bart

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I'm going to buy the GSO for use with both my 100 degree eyepieces. Coma is only mildly offensive in these at f5, but thanks to this thread, curiosity has gotten the better of me and I want to see how much a CC cleans up the views :smiley:

Hi again Damo

I got the GSO for my 100*ers. Helped in the F5 and helped a lot in the F4.5! For small money it certainly is worth it. Saying that, I have found that coma irritates me less as time goes on. Saying that again, sometimes I like the 'clean' view. I'm sure you'll find it useful. Good luck

Barry

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Damo636

Damo636

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Hi Barry

Like yourself, I don't find the coma really bothersome at f5, but as you say, its not a lot of money to settle my curiosity :smiley: Like Russell, I'll probably fix the correct spacers to both eyepieces and use it that way.

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russ.will

russ.will

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From memory, I just spent a night carefully pulling the 30 & 18mm EPs in and out of the CC and carefully refocused each time. When I found the right spot, I measured the gap between the top of the CC and the shoulder of the EP in question. I then bought a single spacer of the length nearest the middle of the two measurements (can't remember the exact measurements, but they were close) from Telskp-express.de for about 29 Euros. Job's a goodun. :)

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John

John

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I'm going to buy the GSO for use with both my 100 degree eyepieces. Coma is only mildly offensive in these at f5, but thanks to this thread, curiosity has gotten the better of me and I want to see how much a CC cleans up the views :smiley:

I'll be interested to see what the result is Damo. I can see just slight traces of coma with my F/5.3 right out by the field stop of the ES 20 / 100 but you have to really look for it and actually pick a suitable star field to see it !.

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Stargazer_00

Stargazer_00

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Like other's im finding coma bothers me less and less even though my scope speed increased from F4.7 to F4.5. Maybe the winter season and it's (hopefully) extended viewing sessions will change my perspective but cetainly initial viewing sessions with my new, bigger dob haven't provided views like a seaside pier swarming with seagulls. Actually the views were rather pleasant. Either I'm not obversing frequently enough to see it or it isn't there. I appreciate my low end magnificaiton is quite alot shorter given the extended focal length of the scope, maybe that's having an effect. Perhaps a lower magnification eyepiece would show more coma.

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Rustysplit

Rustysplit

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I am using the SW CC, the older one that acts as a .9 focal reducer. It works a treat in my F5 dob with my 27mm pan, my 18mm radian and my 12mm delos. It does not seem too fussy with the spacing for visual either. Does a nice job of cleaning up those outer stars.

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