Help with Optics

[Chris85]

Hi everyone,
I was wondering if I could get an opinion on the optics of my North Group ED80 Triplet. I purchased it about 6 months ago with the intention of getting into astrophotography and for the most part has been sitting there unused whilst I slowly built my kit around it. Well the last few weeks I finally got around to using and took a few pics through it, and I'd have to say I'm unsure if it's up to scratch or not.
Now I understand that being a fast scope it's a given that there'd be colour if it's a doublet, but a triplet?
I'v attached below a cropped area highlighting what looks to me like halo's around stars. I used a focus mask and it's a 30s exposure at iso800.
My gut feeling is that I'v got a lemon and I'v let the supplier know but as yet have not got a reply. Should I just cut my losses, stop being a tight git and buy something tried and tested?
Any advice on what I should do would be much appreciated.
Thanks!
Chris

[leon]

Chris probably not a lemon as you say, a single exposure of only 30 secs is not enough to come to that conclusion. IMO

I personally don't like focusing masks, your much better to just use your eyes for focusing.;)

Your tracking seems a little off as well.

It will take you time and many failures to get it to behave the way you want.

Also in my opinion 800 iso is to much stick to about 400 or so and take many exposures and stack them together.:thumbsup:

Through trial and error you will master it, maybe it is not the best scope around but you have to start some where, we all did !!:)

Good luck and don't give up. :)

Leon :thumbsup:

[Tandum]

I've heard a few people whinging about recent scopes from those guys. I read somewhere that they changed glass. Earlier models had Jap glass, newer models don't, but don't quote me. Maybe others who have bought one recently can comment.

As for masks, that's all I use, my eye's aren't what they used to be :)

[PRejto]

Hi Chris,

I agree with Leon....a lot more testing is required before you can draw a conclusion from what you posted! Focusing is really hard, even with a mask. But first I'd ask you how is focusing with the scope when you use it visually? Do you get sharp pinpoint stars? If so, then I would hazard a guess that you should be able to get that as well with your camera? Does your camera filter IR? If not you will get blurry images. Leon is also correct about your tracking. The stars are elongated so something is wrong there and it will be very hard to tell focus problems from drift problems as a little bit of drift will make your result look unfocused. Your polar alignment is probably just not good enough if 30 sec is giving you that much drift.

Anyway, have you read this book by Ron Wodaski? http://www.newastro.com/info/reader_comments.htm

He devotes a very long chapter to the art of focusing!

Peter

[Chris85]

Thanks for the comments guys.

This is just one of many subs I'v taken through the scope. It's only after many nights of trial and error trying to figure it out that I put it to the forum. I originally focused with just using my eyes and only moving onto the bahtinov mask to see if it was just my poor focusing that was causing the colour.
Also I probably chose a poor example, as my mount even with a good amount of time spent drift aligning, still only gives me around 60% usable subs. It was lucky dip as I picked out a pic to show on here. I do have a qhy5 and guidescope ready to go but am having problems figuring out how to mount it on the scope, so hopefully when that happens it should help.

I think I'll just buy a F/flattener to help smooth the frames out and stick with it for now. Probably a bit too hasty in wanting to bin the scope, as there's plenty of other things to work through first!

Chris

[raymo]

Hi Chris,
Firstly, ignore tracking, It's nothing to do with your question
about the quality of the scope.
Secondly, I happened to image M42 the other night, using roughly
the same exposure, as a test of a new camera, and there is no trace of
colour around any star, so the colour in your image is definitely an artifact
of your optical train, either the scope itself, or the eyepiece. I assume that having a relatively expensive scope you would use decent eyepieces
with it. If by any chance you were using a budget eyepiece try again
with a better one.
Thirdly, a star that is focused quite well [not necessarily
perfectly] as yours are, will not show a violet halo through an APO, let alone the unusually extended ones in your image. Even a budget achromat will not show a violet halo because the focus is not quite spot on.
Does your scope show anything more than a suggestion of
colour around the moon. If it's a half decent APO the moon should
be very close to colour free. If it shows any significant amount of
colour I would be onto the supplier again.
I hope this helps
raymo

[Chris85]

Hi Raymo,

I tend to agree with what you say, and so does Keith at Btow after I went in and shown him the same examples. Said it wouldn't even pass for an achro!
Also before using it with my camera, the only eyepiece I used with it was a meade 24mm uwa, so in my eyes everything looked fine. It was only until I started using my camera on it at prime focus that I've noticed the halo's.
My first light was on the moon and I do remember there being colour, but at the time I just put it down to the scope not being at ambient. Maybe I'll try again when the moons up.
And yes I've let the supplier know and he's giving me a response next week.
Cheers
Chris