david_taurus83

+1 for the BBQ cover!

I have the RPi4 with Stellarmate OS on there. Having initially tried the RPi3, the 4 is a huge step up in performance. Platesolving takes a few seconds using the offline guider. Still needs a few bugs ironed out but very pleased indeed. I let the RPi4 run everything and I monitor over VNC Viewer.

I've made another interesting observation on the eternal (infernal?!) quest for round stars! Lets take @ollypenrice's handy sketch below:

The answer looks simple. Adding glass between the corrector and the camera increases the light path/optical distance so we add a spacer to move the camera further away. I have never had much luck with this method. My attempts explained in the top post show this.

However, optical distance and physical distance can be 2 different measurements. Lets assume the required distance above for the corrector to perform optimally is 55mm. With no filter in the light path both the optical and physical measurements are 55mm so everything is perfect. Lets now add in an Astrodon filter at 3mm thick. Though the physical distance remains unchanged at 55mm, the optical distance has increased by approximately 0.33 the thickness of the filter, so 1mm, up to 56mm.

Any rationally thinking person will look at this and see the need to add 1mm to the spacing requirements so that the focal point matches the optical path. 

Thinking about it though, are reducers and flatteners not designed with an optical distance in mind? In the case above with the added Astrodon filter, the optical path is too long for the corrector to perform even thought the physical distance remains at 55mm. The focal point isn't determined by the distance from the corrector to the camera nor should it be by adding a 1mm spacer. The focal point is determined by the movement of the focuser on the OTA. So in the above scenario, we need to reduce the physical distance from 55mm down to 54mm in order to achieve an optical distance of 55mm as per the corrector specifications.

Case study:

At the weekend I switched back to my William Optics GT71 with the WO Flat6A II reducer. This reducer has an adjustable ring and gives from 0 to 11mm extra spacing depending on which scope its used on. It is designed with a Canon DSLR in mind so needs 55mm distance from the shoulder PLUS 9.3mm spacing on the adjuster to match the GT71, as quoted by WO. As I've already mentioned, I've not had much luck working with these quoted figures and adding spacing to take into account Baader filters (2mm) in the filter wheel and 2mm sensor cover glass.  I've always thought I needed to add ((2mm + 2mm)/3) 1.33mm to the physical distance.

Well this weekend I tried the opposite. I took 1.3mm away from the distance so worked with 55mm from shoulder plus 8mm on the reducer.

Stack of 14 x 900s OIII subs:

Top left

Top right

Bottom right

Bottom left

Centre

I have never gotten the corner stars this good before so it adds a lot of weight in my eyes to the theory explained above. Next time I give the 102 a whirl I'm going to try the same and reduce the physical distance and see how I get on. For the time being it would seem that I have, touch wood, found the sweet spot for my main imaging setup....

Hope this helps anyone else stuck down the rabbit hole as well.

David

Second attempt.

This is take 1 of my attempt at the North America Nebula. I followed the excellent tutorial on Light Vortex Astronomy to process this. It's a really great tutorial and I've picked up a few tips to use again but I think I focused too much on trying to bring out the OIII signal and the colour has gone a little awry. It could do with more red imo. What I really hope to do is to take some RGB on the stars and figure out how to add them in and try and reduce the OIII halos. Will have another go at processing this again I think. Comments, criticism and tips welcome!

Also, I'd like to say a massive thank you to Adam @tooth_dr who very kindly offered to lend me his Optolong Oiii filter to try out as my own Baader 8.5nm was giving me really bad, large circular halos on the brighter stars. The Optolong filter still produces slight halos but no where near as bad as the Baader. My processing has probably exacerbated them on the other stars as well! Thank you Adam 👍

William Optics GT71 at F4.6 (336mm)

ASI1600MM

31 x 900s Ha Baader 8.5nm

25 x 900s OIII Optolong 6.5nm

14 hours total integration

Did you do a new calibration in PHD seeing as you haven't imaged in a while?

The Lum looks perfect but I dont know what's going on with that Ha. Did you buy it new? Can you ask for a replacement as I wouldnt be happy with that unknown artifact on the filter surface.

I more or less started the hobby with a goto mount. Since then, I have bought an AZ4 just so I can do it manually!!!😁

Much more fun! Spent half an hour one evening looking for M1. Trying to star hop by using Sky Safari as a guide. Was ecstatic when I found it.

I had a Skytech CLS CCD filter in my modded 600D.

See below 10s shot with a 50mm lens at F1.8, with and without filter.

No way was I processing that LP out.

That shape of the vignetting certainly looks better but that's under exposed. The K value on the bottom should be around 0.3 for a well exposed flat. You can change the settings for it to display 16 bit info but that's just personal preference.

If I was you, I'd take a series of daytime tshirt flats with all the filters and see how they come out. If the others come out ok then you can look at why the Ha might be producing the flats like it is.

Also, you should be trying to expose for longer than 0.1 second for flats. I try and do all my flats at around 5 seconds by dimming the light source for each filter until the histogram is around a third of the way from the left. Or try to get the mean value to around 20k/22k if using 16 bit values. I can use a single master flat dark that way to dark calibrate all the flats.

43 minutes ago, michaelmorris said:

What length of time would you describe as "a good nights session"?

5/6 hours. My PSU that I use now has an ammeter and it doesn't go over 2 amps usage so for a 12ah pack 5/6 hours was about right.

Do the other filters produce better flats?

So they dont calibrate out the amp glow? What's giving you headaches?

Yes, is that actually in the filter cell?

I've never seen that Mount Control Setup box. You should look for the EQMod setup or configure option. You should select HEQ5/EQ6 as the mount, or something like that.

How are the darks not working?

What is that protrusion? Might be the issue.

What do you mean your trying to get them to work? How are you applying them in your workflow?

8 hours ago, Anthonyexmouth said:

It's not the long usb cable as the problem is the same when I take the laptop to the mount and bypass it. 

I've got the startech usb3 hub on the mount. So it's a good hub. 

Just ordered another startech hub on Amazon to at least see if that's the problem, can always send it back after the test

 

I'm not suggesting it's the cable or the hub that's at fault. Saying it may well needs it's own separate connection to the laptop. You say the 294 works fine on it's own plugged directly into the laptop. Have you tried then adding the other devices into another USB port at the same time?

I've had all these sorts of issues myself. The reason I suggested the above is it's the only single cable option I have found to be viable.

Their temperamental devices at best. I'd try the second cable to see if that works.

If that works and you still want to stick with a single cable from outside to inside I can recommend the Startech USB2 hub (4 slots) to CAT5 ethernet. Runs my mount, focuser, both USB3 cameras and filterwheel without skipping a beat.

Fyi I never had luck with my old ASI120 plugged into the hub on the ASI1600. It would loop a couple of frames in PHD and then timeout. The only thing I use that hub for now is the filterwheel.

10m is a long way for a cable and 2 fast frame cameras. Is the cable only USB2?

Is there a way to connect your 290 with the other stuff and the 294 separately to it's own USB port on the laptop?

Looks like some sort of internal reflection. Do all the filters produce this with flats?

Dark calibrate the lights and see if it removes them?

Does look like some sort of reflection. Is it there in all images over different targets?