New telescope problems

[MimasDeathStar]

Hi I'm really sorry to bore you all with the inevitable but I'm having a spot of bother using my new scope and was hoping someone could advise! 

I received a new opticstar ar80s gold f7. 5 yesterday and have been out with it this evening. But I can't seem to get it to focus on anything. 

It's OK on fainter stars but on brighter stars (altair and vega I think!) i'm getting what looks like a massive mess white halo that's taking up half the field of view! It's perfectly circular and reasonably well defined at the edges. Obviously I'm no expert but that doesn't seem right to me! 

The circle is biggest when the star in the middle is at its most tightly focused but as I move away from focus the star itself drifts out of focus and the circle begins to shrink?

I know a little about photography so I'm fairly sure I can tell when the star is in focus. I read online about star tests too - I'm getting a little cross pattern as it drifts out of focus and when I go further I'm getting rings "diffraction rings?" that are OK but slightly elliptical. 

I don't get any of these rings when I go backwards from focus as everything just fades into the massive orb like circle. 

I've done some common sense checks: there's no wrappers or films or anything on any surfaces. I left it outside to cool for an hour before I used it too. I ordered a diagonal from opticstar and a 30 and 10mm Plossl lens but it does the same thing with both. I also have an older plasticky diagonal and a Super Wide field MA 20mm eyepiece that I tried and they all did the same thing. 

There wasn't any dew on the lens - I shone a torch down it and couldn't see anything broken so I can only assume I've made a massive beginners error somewhere. Can anybody help me? 

Many thanks apologies for the daft question! 

[Ruud]

1 hour ago, MimasDeathStar said:

i'm getting what looks like a massive mess white halo that's taking up half the field of view! It's perfectly circular and reasonably well defined at the edges. Obviously I'm no expert but that doesn't seem right to me! 

The circle is biggest when the star in the middle is at its most tightly focused but as I move away from focus the star itself drifts out of focus and the circle begins to shrink?

This sounds like a very out of focus star with the bright spot in the middle being a positive interference effect.  When the circle shrinks you may actually be getting closer to focus. Can you make the big circle shrink to a point?

1 hour ago, MimasDeathStar said:

I know a little about photography so I'm fairly sure I can tell when the star is in focus. I read online about star tests too - I'm getting a little cross pattern as it drifts out of focus and when I go further I'm getting rings "diffraction rings?" that are OK but slightly elliptical. 

I don't get any of these rings when I go backwards from focus as everything just fades into the massive orb like circle. 

Now I think  you found proper focus. In focus you should see a point of light, close to focus (inside and outside of it) you should see lots of rings.

That you see a cross at best focus and an ellipse outside of focus may point to astigmatism. If the ellipse flips in orientation when you move from outside of focus to inside of focus that confirms astigmatism even more. However, you just get an ellipse on one side of focus and a blur on the other. Most likely there is more going on than just astigmatism.

1 hour ago, MimasDeathStar said:

I ordered a diagonal from opticstar and a 30 and 10mm Plossl lens but it does the same thing with both.

Could it be that the telescope needs the diagonal to be able to reach focus? Were you using the telescope without diagonal in the big circle from the first quote above?

---

My guess is that something is definitely wrong with the telescope. Put it through another test: How does it perform on terrestrial targets? Try some contrast rich targets from about 50 metres to a few hundred metres. Do the images snap to focus and do the closer targets appear contrasty and crisp, especially when you use the 30mm Plössl?

More knowledgeable members will be along soon.

[johninderby]

I’ve had both the 80mm and 90mm Opticstar achros and both have had very good sharp optics and stars were pinpoint. It does sound like you are way out of focus and seeing an airy disk.As you move the focuser from one end of focus travel the large airy disk should shrink until you get a pin point star then as you continue to move the focuser another airy disk should start to appear and get bigger.

 

[MimasDeathStar]

6 hours ago, johninderby said:

I’ve had both the 80mm and 90mm Opticstar achros and both have had very good sharp optics and stars were pinpoint. It does sound like you are way out of focus and seeing an airy disk.As you move the focuser from one end of focus travel the large airy disk should shrink until you get a pin point star then as you continue to move the focuser another airy disk should start to appear and get bigger.

 

Yes it is very confusing I'm not sure what I'm doing wrong (knowing me it'll be something extra extra daft) 

The problem is that I am getting a pin point star - it's just sitting in a massive big splodgy halo! 

I went out last night and had another go at the moon - I was getting a sharp focus on the moon but the whole view through the eyepiece was like the moon was sitting on a slightly off-white table cloth, it was difficult to make out where the moon stopped and the sky began. But the features were super sharp. 

Im sure I've done something silly and obvious, I'll have a cup of tea and then investigate! 

Many thanks for the replies sorry for such obvious beginner questions. 

Edited September 14, 2019 by MimasDeathStar

[MimasDeathStar]

Update - as suggested I have tried this morning on distant objects. I'm quite lucky to have a horizon that is a good couple of miles away so tried some trees and pylons in the distance. 

Sharp focus was more or less achievable but the contrast was terrible, it was like looking through a piece of tracing paper! And I was getting a weird ghost like fuzz around high contrast things like pylons and lamposts.

Its almost like what you'd expect from a really dirty or greasy lens I just don't understand it! 

Just to make sure I've been all the way through the focus travel from one end to the other but it only focuses once. 

Edited September 14, 2019 by MimasDeathStar

[Skipper Billy]

If you look through the scope without an eyepiece in does it look clear or hazy ?? (looking at the optics rather than through the optics). Do this front to back and back to front.

It should look gin clear.

 

Edited September 14, 2019 by Skipper Billy

[DaveL59]

thinking about your earlier remark that out of focus rings are elliptical rather than round, could this be collimation of the lens elements I wonder? The Tal100RS I have gives circular discs and sharp images so that's a possibility to consider, perhaps. No idea how you'd adjust that on your scope or if you've any collimation eyepieces to work with.

[dweller25]

I would discuss this with the supplier as it sounds like something may be wrong.

[Ruud]

1 hour ago, MimasDeathStar said:

tried some trees and pylons in the distance. 

Sharp focus was more or less achievable but the contrast was terrible, it was like looking through a piece of tracing paper! And I was getting a weird ghost like fuzz around high contrast things like pylons and lamposts.

As Dave says, it's time to talk to the dealer. Refer them to this thread.

[johninderby]

Could have been damaged in shipping but I’ve found that Opticstar has great customer service so it will get sorted out. 

I once sold a scope that I’d originally bought from Opticstar and the buyer found that the finder, that I’d never even used, was defective and Opticstar replaced it free of charge for the buyer. Top service. 👍🏻

Edited September 14, 2019 by johninderby

[Ben the Ignorant]

3 hours ago, MimasDeathStar said:

Sharp focus was more or less achievable but the contrast was terrible, it was like looking through a piece of tracing paper! And I was getting a weird ghost like fuzz around high contrast things like pylons and lamposts.

Its almost like what you'd expect from a really dirty or greasy lens I just don't understand it! 

A really badly derotated and/or decentered objective lens could cause that. I bought (and still have) a cheapo 80mm achro doublet that was so derotated and decentered the image had an horrible blur to it. Rotation marks were present on the lenses' edge so that was quickly solved but the centering problem required adding radial screws to the cell. Not something you should do on a classier scope that's still under warranty, though.

Edited September 14, 2019 by Ben the Ignorant

[MimasDeathStar]

4 hours ago, Skipper Billy said:

 

Thanks for the replies everyone thats really useful - I've got in touch with Opticstar hopefully they can help. 

Not the illustrious start to astronomy I'd hoped for haha! 

Thanks again 

[Alan64]

Would it be possible for you to post an image of the objective, like this...

[MimasDeathStar]

On ‎16‎/‎09‎/‎2019 at 22:21, Alan64 said:

Would it be possible for you to post an image of the objective, like this...

Really sorry - I missed your post I've not got hang of the notifications yet!

[MimasDeathStar]

Hello all - apologies I forgot to finish this thread off: I sent it back to Opticstar and they were really nice about everything.

They confirmed that it was a fault with the scope - they star tested it and replicated what I was seeing easily enough. Peter said he wasn't sure what was causing it without taking the objective apart. His best guess was that a thump in transit had affected the distance between the lenses or decentred it somehow.

I replaced with a Meade Polaris 70/900 and fingers crossed things going ok so far. As it turned out I think I could really do with a dedicated tripod as my photo tripod doesn't really work with a scope so this looked like a fun package.

Can't thank you all enough for your help and suggestions!

Edited September 27, 2019 by MimasDeathStar

[johninderby]

Glad to hear ypu have got things sorted out. They are very helpful at Opticstar. 👍🏻

[Alan64]

15 hours ago, MimasDeathStar said:

Hello all - apologies I forgot to finish this thread off: I sent it back to Opticstar and they were really nice about everything.

They confirmed that it was a fault with the scope - they star tested it and replicated what I was seeing easily enough. Peter said he wasn't sure what was causing it without taking the objective apart. His best guess was that a thump in transit had affected the distance between the lenses or decentred it somehow.

I replaced with a Meade Polaris 70/900 and fingers crossed things going ok so far. As it turned out I think I could really do with a dedicated tripod as my photo tripod doesn't really work with a scope so this looked like a fun package.

Can't thank you all enough for your help and suggestions!

I do hope you find the new, different one satisfactory.

Incidentally, that image I posted is the objective of my Meade "Polaris" 90/900.