marktownley wrote: ↑
Fri Jul 26, 2019 6:11 pm
I would make sure the ERF is as high up the tube as possible so it intercepts as much of the exit beam from the objective as possible. Aim more like 2/3 up the tube.
The -200mm is so important, I get you're just trying stuff but fundamentally just aim for -200mm in the first place. Just measure it!
Had a look at your website. The camera is a bad choice in it's basic form - 2.4um pixels are way too small. Use the camera in 2x2 binning, the (then) effective pixel size is much better suited and the gain in exposure time will also be on your side.
All this will help!
The centre of the Etalon still is 15mm outwards in the tube - needs to go 15mm inwards to be at 700mm FL.
Have to find a way of doing it, without cutting tube - if possible - as 700mm FL is just 5mm inside the end of the metal tube - luckily - that is why I use that Tin just to see if it was not far off and it is not.
I agree with the ERF distance logic [fact!], the nearest to the lens the less currents, temperature on it and also sharpness should improve too. Problem with this cheap scope, I believe the front shield is actually glued on it - not pressed in! I also noticed is not even straight ...
I have to see if I can take it off, then take lens off ans see if there is another place inside - like the one at 28.5cm from back of tube - that would be great - just avoiding cutting tube and also trying to avoid to buy a 90/100mm to put in front as it is too expensive for me.
The beam at 28.5cm is must be 28.5mm - in fact there is a 50mm hole on that plate.
If there is one at about 30cm from front, beam should be 60mm and hole maybe 72-73mm.
I have to see, when I get time.
Must get or find a 25-30cm dovetail to fit my rings and make telescope less wobbly.
Yes, about the binning, I have used it a few times and you are right, of course - it becomes a 4.8µm + faster acquisitions.
Thanks for your help.