Chris49

Hi Nigella, This is my best effort from March 2017 - not an APOD 😉: EOS7D not modded, mounted on tracking A-VX, 70-300 at 280mm at f/8, best 12 out of 16 - 4min subs at ISO1600. One dark and one bias, stacked in DSS. I found stopping down the lens made a huge difference to the star roundness. Chris

With longer than 90 sec subs, the stars start to become sausages. This is I believe the result of flexure between the main and the guide scope. I have now improved the guide scope rigidity by putting it in rings on top of the main scope, but I haven't had a chance to try this yet - part of the back garden was underwater this morning. 🙁 Your NGC891 is stunning - thanks for showing me what can be done. Chris

I see what you are getting at, but I come back to the HFR values that I get for the stars in the subs with Sequence Generator Pro - these range from 3.5 to 6. When I watch videos of people using SGP, they get values as low as 1.2 so my stars are large at that stage. I suspect they then get bigger still with my attempts at processing, probably because I have stretched them too much. Your comments are certainly making me think!! Thanks Chris

I did watch your video last night and it looks very useful. I'm such a novice with processing that I will need to follow it through step-by-step with an example of my own to understand it. I have CS6 - yours may be a different version but I guess that won't matter. Your star reduction certainly shows an improvement on my picture. Thanks Chris

You are right, they are not. So I was just lucky they came out roughly round! Back to improving the guiding! Thanks Chris

You are right of course, but I think it is a case of "small steps" to make progress without getting discouraged. I am a bit wary of the OAG because people say they are hard to use. I hope to get there eventually! Thanks for the advice. Chris

I'm not too far off then. Thanks for posting your image. Chris

The guide scope is the standard Celestron 50mm finder #51611 and holder that comes with the EdgeHD8 - not very satisfactory as it is not rigid. Guide cam is SX Ultrastar. I have since moved it to rings mounted on a Vixen dovetail on top of the main tube. This is much more rigid and is symmetrical for balance so that should help. Mount is iOptron GEM45 - just getting used to it, but I am impressed so far, way better than my A-VX which had so much Dec backlash that it never came back! Thanks for the encouragement! Chris

There I was thinking 10 minutes processing was a bit excessive - I was hoping my subs were going to be nearly perfect straight out of the camera 😀. Chris

That sounds a really clever technique. There's a lot to this astro stuff when you get into it! Thanks Chris

I don't think it does reject UV, hence my worry that UV might be out of focus and lead to blobby stars. I thought that was more a problem with refractors than reflectors though, although there is the corrector plate I suppose. I do have an LP filter to try, but although Clear Outside says I have Bortle 4, I find that hard to believe! I will search for PS star reduction as you suggest. Thanks Chris

Thank you Carole. I will be more careful next time. So far I have had very little idea what I am trying to do and even less about how to do it! It's all part of the learning curve. Chris

Thanks Vlaiv, that's very helpful. I guess I have been unrealistic up to now. I will work towards what you suggest. Chris

Stacked in DSS, stretched a bit in Photoshop - I may well have clipped off the brighter stars. Chris

A lot to think about here. Clearly I will try to find a place to put the filter and concentrate on improving the guiding. Also maybe I should include the #94242 0.7x reducer - I was trying without because it is the tiny galaxies that I'm really after. Thank you for your advice. Chris

This was 19 out of 30, so a lot were thrown away. I haven't splashed out on Pixinsight yet, I am trying to get something worth processing first! I have made big changes to the setup - moving the #51611 guide scope on to a top bar from the normal finderscope position. That should help balance. Waiting for it to stop raining here! Thanks for your thoughts. Chris

Thanks Dave. Presumably that is with your C11? I've never used a refractor, but people seem to get HFR of ~1.2 with those. Is 3.5 to 6 all I can expect with a reflector?

Thanks Dave, I did give it a bit of curves stretching in Photoshop and I had to suppress the hot pixels by hand - no dark frames - clearly I missed a few. Any thoughts on the need for a filter? Chris

This is NGC891 taken as 19 subs of 90sec on 3rd Dec. using EdgeHD8 at 2032mm attached through the #93644 T adaptor to an SX694C Pro OSC, then stacked in DSS. Why are the stars so big? SG Pro gives the HFR values between 3.5 and 6 - I've tried improving focus, but can't get it better. I've used a Bahtinov mask and I've used the autofocus routine in SG Pro, but to no avail. Is it that I need a UV/IR filter? If so, where in the image chain can I mount it - there don't seem to be any convenient 1.25" or 2" threads to mount it with my setup. Guiding with PHD2 gives me about 1 arcsec or better, but I have some flexure issues. As you will have noted, I have minimal skill at processing! I would be very pleased for any pointers as to what is happening here - don't hold back to spare my feelings, I know there is a long way to go! Many thanks Chris

Just got the chance to try the calibration again. This time, I moved the counterweight bar to horizontal, then clicked on Confirm position 1. It said to slew the RA more than 45 degrees from previous positions, which I did and it then said it had auto-confirmed position 2 and that all positions were confirmed. This gave X=462.1 and Y=665.2 so very close to what I had before. It seems they have made the software even more automatic than in the manual and it knows when it has moved enough to make the calculation. Unfortunately the clouds rolled in again and I wasn't able to check the polar alignment accuracy in PHD2, but I think the calibration has done the right thing now - so a small step forward! Chris

My GEM45 has similar problems with setting up the iPolar - I've started by moving the counterweight bar to horizontal and it doesn't wait for you to press the Confirm Position 1 - it has already pressed it and moved on to Position 2. You start slewing the RA back so that the counterweight bar is pointing down and before you've got there it says "All position confirmed". It seems to give sensible values for the Center of Camera X=461.8 and Y=664.2. I then centered the cross on the dot successfully, but when I checked the polar alignment error in PHD2 it said 37.7 arc-min! I think I have been starting with scope east/ counterweight west, but if we get to see some stars soon, I will try it the other way round - thanks for the suggestion. Chris

I found a thread on cloudy nights https://www.cloudynights.com/topic/513870-cem60-search-for-zero-and-other-stuff/ in which someone took his CEM60 apart and found a combination of pins and Hall Effect sensors that control the Search Zero process. Presumably that is more accurate for setting the zero than doing it by adjusting the clutches by hand and eye, whether you can be present or not. Thank you for your efforts to help. Chris

I don't know if iEQ45 has through-the-mount cabling, but I will try your approach and see how i get on. Thanks Chris

I had read it, but sadly I hadn't understood it - hence the request for guidance. My anxiety was that you could tangle up the through-the-mount cabling by moving the Zero Position. The Goto Zero Position takes you to where the mount thinks is Up and North, but not if the clutches have moved. The Search Zero command (by some clever method that I do not understand) sets the mount to Up and North even if the clutches have moved. But doesn't this mean that the wiring risks getting wound up? Apparently not. I think I now know what to do but without understanding why. Chris

I have recently bought an iOptron GEM45 (from FLO) and I am a bit mystified by the Zero Position. The hand control gives you the options of "Goto Zero Position" and also "Search Zero Position", but they appear to do the same thing! Does the mount have sensors like the Home position of a Paramount, which sets the axes to an exact hardware position, or is it something else? I guess this is the same for other iOptron EQ mounts so maybe a skilled user can enligten me. Many thanks Chris