Craig a

After using a guidescope with a mirrored telescope I’m my case a Newtonian, I switched to OAG and came to the conclusion that all mirrored telescopes should use OAG’s to eliminate differential flexure, my images changed immediately when going over to OAG 

On 05/10/2021 at 18:03, Ricochet said:

In my experience, I don't think so. Maybe carefully examining a photo you might be able to spot something but close enough is probably fine. If you want something really accurate I think I've seen commercial masks for Skywatcher scopes somewhere, Telescope Express perhaps.

As I don’t have access to a 3D printer I looked at ts service and you were correct I ordered one from there for my 130pds should be here in a few days 

On 27/09/2021 at 09:44, vlaiv said:

What scope are you using?

One thing to try would be to add long dew shield kind of shroud made out of very dark material (flocked on the inside) and take your flats like that.

Flat panels work well with baffled and flocked scopes. Some scopes can't cope with that much light hitting inside of the scope at different angles. Newtonians are prime candidate for this sort of behavior.

Interesting that is because I was getting some horrid circle gradients using an led tracing pad on my 10 inch f4 Newtonian with the pad laying straight ontop of the scopes aperture even with a t shirt it must of still been too bright even though the scope was flocked and has baffles the light still must of been bouncing around in there 

I ditto what tomato said, I did the exact same thing when setting up my zwo OAG, pain to setup but one done it shouldn’t need doing again 

So is it just the very edge of the mirror coating that is the offending area? Just wondering if somthing can be done to it without using a mask and shrinking the diameter of the mirror slightly? 

8 minutes ago, Ricochet said:

Ok, perhaps a picture will help. Look at the image below.

• The left hand star shows what your stars currently look like, with both mirror edge diffraction spikes and clip shadows.
• The middle star shows what your stars will look like if you get rid of the clips.
• The right hand star shows what your stars will look like if you mask the mirror edge.

It's not the shadows that are the problem, it is all the excess spikes.

 

I'm a solely visual, but even then masking the mirror edge is the single best upgrade that I have made. It's also the cheapest, as my mask is just made from black card.

Yes that helps loads thanks, I will have ago at making a mask too, is it critical to get the masks inner edge perfect? 

1 hour ago, Ricochet said:

That is my point. The mirror clips are not causing the issue, they are preventing the issue at three points. If you take them off the problem becomes worse. 

We’re not on the same wavelength here I don’t think I’m not on about the bright diffraction from the mirrors edge but the dark ghost pattern off the clips is what I want rid of 

7 minutes ago, Skyline said:

Or buy a refractor.

😂 and where’s the fun of tinkering with one of them 

That’s what I mean the scatter/diffraction from the mirror clips causing the pattern on brighter stars, I’m not a fan of it and looking for a way of getting rid without making a mask to cover the whole perimeter of the primary covering the clips 

Thank you for your reply, any special silicone I need to use? High modulus, low modulus? I was thinking of aquarium silicone as it’s designed for glass? 

Hi all I’ve seen people making masks to cover the mirror clips of Newtonians to eliminate the shadow they cast on brighter stars, but I’ve also seen people totally do away with them and silicone the mirror onto the mirror cell, I was thinking of doing the same to my 130pds using the silicone method to secure the mirror doing away with the clip. Has anybody done this to their 130pds and how secure is the mirror when the silicone is cured? Does this affect the mirror in any way? 

Glad you got it sorted, it’s a good start , you can always add more data to it as the autumn and winter draws on

No problem let us know how it goes 

Yes you go into raw/fits digital development process settings, then in the fits tab check the little box at the top  then select generic rggb in the camera selection, that should sort it don’t worry about any colour cast when it’s done that is sorted out in post processing 

Did you debayer correctly I’m dss? 

From what I could find out it shifts it out by approx 10mm 

6 hours ago, peter shah said:

One of my tricks for that is to use a gaussian curve with a flat line at mid range to high. It helps retain star colour and keeps their brightness under control.  The main disadvantage is it keeps contrast very low so there is a need to use other methods of contrast enhancement to compensate.

What is a Gaussian curve Peter if you don’t mind me asking? 

Excellent stuff, what is that ring around a star close to sadr? Is that a planetary nebula? Don’t think I’ve seen it before

A really super image, bortle 1 sky’s! I can dream, the view of the Milky Way must of been mind blowing 

Still don’t know why zwo set the default offset to 70 though when I’ve seen quite a few people using offsets ranging from 10-25 🤔

1 hour ago, bottletopburly said:

I’ve just done some data with darks , I will try without , which seem fine with 

Apparently from what I’ve read the 533 sensor has no fixed pattern noise so darks are not needed to get rid of it and hot pixels are gone with dithering and sigma rejection, also using darks reduces SNR, I’m not an expert but just quoting what I’ve been reading, also flat darks are not needed either just bias subtracted flats is fine with the 533, 

hopefully someone with abit more knowledge than me can set me straight on what I’ve read 

I’ve just read an interesting thread over on CN, that darks are not recommended for the 533 also no need to go higher than 15 offset, as no one has any idea why zwo decided on such a high offset, now I’m really confused 😂

I agree with above comments, I think OAG is a must with any scope with mirrors, I had issues with stars in my images with a guidescope on my 1000mm f4 Newtonian switched to OAG and boom all sorted, differential flexure was eliminated, I’d never go back to a guidescope again 

Forgot to add I live on the west coast of England between two river estuaries, the Dee and the Mersey so I get pretty damp 

I keep my gear permanently setup bar camera literally outside all year round under a telegizmos 365 cover I take the cover off every now and then when it’s nice to let it breathe, been outside for 3 years and not noticed any damage or degradation, so in a shed I would say go for it, scopes get drenched when dew and frost is about, they are designed to be outdoors after all