First Light with GT81...Markarians chain... DSLR

[StargeezerTim]

I suppose its a 'second light' in truth as my first attempt had heart shaped stars and didn't deserve an outing here! 

This is from last night. Managed 14 X 5 min subs (ditched one of them) before it disappeared behind my house. Stacked in DSS and processed in PS and a gradient removed in Pixinsight Lite DBE function.

I don't know if I'm over critical and worried about the scope but I'm not that pleased with the star shapes. I know there is some rotation on the edges that needs dealing with but even the stars in the centre of the image seem a bit 'square' like or 'boxy' to me, but this is the first time I have used a Refractor. Comments and suggestions welcome! 

Here is the full image:-

 

Here is a heavy crop of the centre:-

 

Does this look normal?

 

 

 

[ronin]

Something on the "lower" edge of the stars that seems to extend them a little into the "boxy" shape that you mention.

What is the camera and what is the focuser? Just a thought that if a DSLR and the crayford if weight is a little of an issue.

Do you have a flattener or reducer in the path.

I assume you are guiding, what is the guider = seperate or OAG ?

Never sure about the "standard" comments of pinched optics or spacers intruding. Have read more then one where these supposed problems were not the problem. So I would not consider panicking in any way.

Ooops: Must read the subject title, it says DSLR. I think I got to the GT81 bit and no further.

[xtreemchaos]

thats a great image Tim, i had a simerler problem, it turn out my scope was slightly off balance for imaging, i made it slightly weight end heavy and it sorted it. thanks  charl.

[StargeezerTim]

7 minutes ago, ronin said:

Something on the "lower" edge of the stars that seems to extend them a little into the "boxy" shape that you mention.

What is the camera and what is the focuser? Just a thought that if a DSLR and the crayford if weight is a little of an issue.

Do you have a flattener or reducer in the path.

I assume you are guiding, what is the guider = seperate or OAG ?

Never sure about the "standard" comments of pinched optics or spacers intruding. Have read more then one where these supposed problems were not the problem. So I would not consider panicking in any way.

Ooops: Must read the subject title, it says DSLR. I think I got to the GT81 bit and no further.

Should have said... I am using the 0.8 WO flattener and reducer designed for the scope. Guiding is with Lacerta MGEN with guidescope.

[Davey-T]

Is it in all the subs ?

Dave

[ronin]

Accept my apologies, I also never seemed to read your signature with equipment at the end of the post. One of those days of not seeing the wood for the trees, or Specsavers needs a visit.

Something says a small internal reflection (just not sure why), Canon will have a shiny metal ring where you attach the DSLR to the rest of the equipment - are you blocking off the rear view finder on the DSLR ?

Pretty sure this same problem has been asked previously and so I would expect someone to come along and say "Had that, solved it like this". I cannot recall any more.

Is Herts/Essex boarder Bishops Stortford ?

[StargeezerTim]

36 minutes ago, Davey-T said:

Is it in all the subs ?

Dave

Yes 

[StargeezerTim]

35 minutes ago, ronin said:

Accept my apologies, I also never seemed to read your signature with equipment at the end of the post. One of those days of not seeing the wood for the trees, or Specsavers needs a visit.

Something says a small internal reflection (just not sure why), Canon will have a shiny metal ring where you attach the DSLR to the rest of the equipment - are you blocking off the rear view finder on the DSLR ?

Pretty sure this same problem has been asked previously and so I would expect someone to come along and say "Had that, solved it like this". I cannot recall any more.

Is Herts/Essex boarder Bishops Stortford ?

Yes...

[toxic]

nice image Tim

it loooks like reflections from the lens clips if it is then you can just cut a bit of black plastic from the bottom of a plant pot in the shape of a ring about 5mm to 8mm wide so it fits just in front of your primary lens and see it that helps it will act like a baffle.

 

[StargeezerTim]

1 hour ago, toxic said:

nice image Tim

it loooks like reflections from the lens clips if it is then you can just cut a bit of black plastic from the bottom of a plant pot in the shape of a ring about 5mm to 8mm wide so it fits just in front of your primary lens and see it that helps it will act like a baffle.

 

Thanks Chris,

I just read another thread where someone said they had stars like 'squashed 50p pieces' which is almost an exact description of my stars. Not sure I should have to cut up plant pots to cure it, and wouldn't that also mean I lose some field of view? (the reason I wen't for this scope!).

Cheers, Tim. 

[toxic]

just a test to see if that is the problem at least you can rule it out if it isnt that hope you get it sorted 1 way or another 

[Pompey Monkey]

I have the same issue on my (second hand) Star 71, and I'm only using a KAF 8300 chip. I'm still trying to get to the bottom of it. Here is a crop from the corner of one of my images:

If you bought your GT 81 new, I'd advise getting a replacement asap.

[StargeezerTim]

42 minutes ago, Pompey Monkey said:

I have the same issue on my (second hand) Star 71, and I'm only using a KAF 8300 chip. I'm still trying to get to the bottom of it. Here is a crop from the corner of one of my images:

If you bought your GT 81 new, I'd advise getting a replacement asap.

Snap! Is yours a WO or TS version?

I did buy it new Paul and I'm sure I will be able to return it without issue, but just want to make sure its not a case of 'operator error' before I do that. Trouble is, I also bought some accessories from other retailers (e.g. Bhatinov mask, Diagonal and RDF with a WO fitting) that might not be so willing to provide a refund, but I'll have to see. Its also annoying as  i spent months and months deciding on this scope before committing to it.

Cheers, Tim. 

[Pompey Monkey]

39 minutes ago, StargeezerTim said:

Snap! Is yours a WO or TS version?

I did buy it new Paul and I'm sure I will be able to return it without issue, but just want to make sure its not a case of 'operator error' before I do that. Trouble is, I also bought some accessories from other retailers (e.g. Bhatinov mask, Diagonal and RDF with a WO fitting) that might not be so willing to provide a refund, but I'll have to see. Its also annoying as  i spent months and months deciding on this scope before committing to it.

Cheers, Tim. 

Tim,

Mine is the WO version that came without the tilt adjuster. I tried one of those and not much happened, apart from getting a tilted field! I took the scope to Steve Collingwood last week who very kindly took a look at it. Unfortunately (or fortunately?) we could find little wrong with the optics, even at a very high power with the autocollimator. Steve suggested having a look at the draw-tube alignment, so I'm currently pursuing this route. However, there is not much adjustment to be made using the fitted components and I'm contemplating some serious alterations if the initial experiments show promise.

BTW, the draw-tube guide arrangement was a bit of a let-down when I saw it - it's just some teflon pads with a couple of brass adjusters on one side. There are two grub screws further out that could be made to push the draw-tube to one side or the other, but they are too short to reach properly and I'm waiting for the postman to bring me some longer ones!

[StargeezerTim]

28 minutes ago, Pompey Monkey said:

Tim,

Mine is the WO version that came without the tilt adjuster. I tried one of those and not much happened, apart from getting a tilted field! I took the scope to Steve Collingwood last week who very kindly took a look at it. Unfortunately (or fortunately?) we could find little wrong with the optics, even at a very high power with the autocollimator. Steve suggested having a look at the draw-tube alignment, so I'm currently pursuing this route. However, there is not much adjustment to be made using the fitted components and I'm contemplating some serious alterations if the initial experiments show promise.

BTW, the draw-tube guide arrangement was a bit of a let-down when I saw it - it's just some teflon pads with a couple of brass adjusters on one side. There are two grub screws further out that could be made to push the draw-tube to one side or the other, but they are too short to reach properly and I'm waiting for the postman to bring me some longer ones!

Best of Luck Paul!

With my engineering skills (irony!), I would be better off returning it! Tim. 

p.s. Is that Steve from FLO?

[Pompey Monkey]

1 hour ago, StargeezerTim said:

Best of Luck Paul!

With my engineering skills (irony!), I would be better off returning it! Tim. 

p.s. Is that Steve from FLO?

It's Steve from SCTelescopes

[Davey-T]

You could lash out on one of these "only" 240$ plus postage 

It does say guaranteed no image shift.

Dave

http://www.williamoptics.com/accessories/2R&Pfocuser_feature.php

[Pompey Monkey]

3 minutes ago, Davey-T said:

You could lash out on one of these "only" 240$ plus postage 

It does say guaranteed no image shift.

Dave

http://www.williamoptics.com/accessories/2R&Pfocuser_feature.php

I don't think it would fit around the internal OTA which actually sits inside the draw-tube! I'm not convinced that the quality would be any better either. But thanks for the suggestion

[Davey-T]

1 minute ago, Pompey Monkey said:

I don't think it would fit around the internal OTA which actually sits inside the draw-tube! I'm not convinced that the quality would be any better either. But thanks for the suggestion

It says it's made for the GT81.

Dave