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  #21  
Old 24-12-2018, 05:23 PM
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A small update.

I have replaced the focuser with a Feather Touch 3.5 inch, wow, what a bit of kit that is and I have also replaced my 12nm QHY narrow band filters with some Baader narrow bands of about 7 and 8 nm, which I have blackened the edges, of including my LRGB set, so Baaders all round.

I have only had the chance to do some focus testing and tweaking as the step size had changed a tiny bit and although I tried both objects that were originally a problem and didn't see any issues it is still too early to tell.

Thanks to everyone I have dealt with lately through IIS Classifieds, I hope to reward you all with some really good images.

Updates as soon as the weather allows, here's hoping it is good news!
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  #22  
Old 24-12-2018, 09:04 PM
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Stonius (Markus)
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So it could have been filters or the moonlite focuser?
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  #23  
Old 25-12-2018, 11:19 AM
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No Moonlite, was the stock WO focuser. My money would be on the focuser to be honest although too early to tell.
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  #24  
Old 27-12-2018, 06:54 PM
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So...still there!


I have noticed that it is the shape of something and I can see a screw or a hole in something so it must be the edge of something reflecting back.



Also, as it seems to look slightly different in each filter, would that mean that it is before the filters, like in the flattener perhaps. I am using a WO Adjustable PFlat IV.



Ive tried looking down the tube and with the torch and the tube is very well baffled including the F/Touch focuser therefore I think I'm going to concentrate on the camera and filter wheel etc.


Any other feedback before I head up with a heap of adapters to get the right focus distance and tear it apart?


First image is green, second one is lum.
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  #25  
Old 28-12-2018, 10:26 AM
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Maybe it's obvious, but have you tried just pointing close to a bright light so you can get real time feedback on the camera? Eyeballing it with a torch may not give the same effect, besides, you'll have your hands free to manipulate things and see if they move (ie, rotating just the camera and seeing if the grub screw rotates with it).

Might help you zero in on a solution faster than using the stars?

Let us know. I'll be interested to hear the solution.
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  #26  
Old 28-12-2018, 12:39 PM
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Hi Markus,

That would be yes to that. I've tried the light on the wall of the obs, my flat box, a really bright variable torch and my weak wind up torch, none of which produce this result. The strange thing about it, too, it does it when I point to NGC300 or witches head but not the Tarantula or M42. It only seems to be when the scope is right up.

I'm going to try the flattener, as it rotates as well as adjusts, to see if the reflection moves.

I will certainly share the results when I find what it is.
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  #27  
Old 31-12-2018, 10:30 AM
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The culprit has been busted, apprehended and charged!

I would seem that it is the flattener.

I have tested with and without on the same two objects that give issues and it is clear that when the flattener is installed I get the issue, no flattener, no problems.

The inside of the flattener is quite lightly coloured, which seems unusual. I am looking at some pot belly black paint to paint the inside before I retest it.

The flattener seems to help more with guide stars than the actual image itself, although I have not had the chance to do any long exposure tests to check the stars in the corners. Do I really need a flattener?

I will post some images later when I can get time to do something with it. I am going to image a bit with out and see what happens.

Last edited by Bart; 31-12-2018 at 03:28 PM.
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  #28  
Old 31-12-2018, 01:46 PM
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Ah, that's good to know. Thanks for the update
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  #29  
Old 01-01-2019, 11:21 AM
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Well, looks like I may have been wrong. I have painted the inside of the flattener with no success. I have also tried turning the filters around with no result. The only thing that works is to remove the flattener from the imaging train so I'm going on a long shot here but it must be a reflection issue between the flattener and the filters.


The flattener is really good at resolving guide stars for the OAG, as for the star field, I could nearly get away with it.



At the moment, it is no flattener until I can be bothered to get adapters made for the 2.5" TS full frame unit I purchased here.
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  #30  
Old 01-01-2019, 05:48 PM
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Hi,
Which field flattener was the first one, any close up photos of it, in and out entrence?

The new TS field flattener, is it the Riccardi they sell or?

I have the 2.5" Riccardi, in my setup with a TS130 APO refractor and a off-axis guider it works well, but can not handle full frame sensors. I have recently changed it to a 3" field flattener.

In the old setup with the 2.5" I had to modify the adapters to get better control of the vignetting.

http://www.astrofriend.eu/astronomy/...refractor.html

But I think you have a smaller sensor and then you will not get these problems.

Which OAG do you have?

Lars
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  #31  
Old 03-01-2019, 08:28 AM
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This is the TE flattener that I am thinking of using.

https://www.teleskop-express.de/shop...otography.html

Here is the flattener that I have been using.

https://williamoptics.com/hot-tech-a...ucer-flattener

I guess it doesn't suit my camera/ filter wheel setup.
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  #32  
Old 03-01-2019, 10:14 AM
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Hi
The new TS field flattener should work if you can use your focuser threads, is it M68?

The WO looks a little bit strange, does it has only a 2" connection? They say that the lens opening is 50 mm, but with only a 2" connection you can't use the full potential of it. The data is strange to me, in one place it say it covers fullframe and at another place they say the image circle is only 35 mm. A full frame sensor needs at least 44 mm.

My Riccardi field flattener says to have an image circle of 42 mm, with my demand I say it's closer to 35 mm. But it's some variation also to wich telescope you connect it to.

To fit an OAG and fullframe sensor make it more complicated. Needs bigger image circle if you should not loss light to the guide camera. To a full frame sensor and OAG I will say 50 mm imaiisge circle is good and all openings must be more than that between the telescope and field flattener. It's a light cone. A 2" tube doesn't work, M68 adapters are ok.

But you don't have a full frame sensor, your problem is reflections.

The WO 2" connector is strange, can't you connect the WO field flattener without going over the 2" tube, more use a M68 thread? It could be a lot of reflexions inside that small 2" diameter tube but long.

Lars

Last edited by Astrofriend; 03-01-2019 at 10:24 AM.
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  #33  
Old 04-01-2019, 07:11 AM
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The snout of the WO flattener screws off, allowing you to use it by directly screwing it onto the focuser.


I am using a camera with a KAF8300 sensor so I do not need full frame.


I am hoping I will not have reflection issues with the new flattener.
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  #34  
Old 04-01-2019, 11:02 AM
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Hi Bert,
Did you use it without the snout and still got the reflections?

Good that you have a smaller sensor, much easier to connect an oag without getting bad vignetting problems.

I wish you good luck with the new field flattener.

Lars
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  #35  
Old 08-01-2019, 11:30 AM
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This has me keen to try to chase down a reflection, I only recently started imaging with any seriousness. Just before the new year I gave my old 350D a last go on the horsehead and flame and the reflection from Alnitak when it is just out of frame is absolutely spectacular. I tried it again with the new camera (ASI 294) and it is just as spectacular. Think in terms curved rays of light, coming together in a big ellipse if you bring Alnitak in to view at the edge of the frame. There is a similar effect on my M42 shot in the beginner section.

I will have to try all of the above by way of tests to look for bright surfaces, and do a test without the reducer I have in the train now.
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