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schmeah

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Posts posted by schmeah


  1. I suspect you would be more than happy with Avalon. My M Uno has served me well over nearly five years of ownership. It has been essentially maintenance free ( no gears to remesh or grease ), responds superbly to guiding, and has been reliable in every way. I’ve also not had any major issues with wind, though don’t image typically with winds > 10MPH. 

     

    Derek


  2. So just for clarification, was your positioning correct from the start? And with the controller you have to rotate the forks 180 degrees in RA to point the scope towards the Southern meridian after polar alignment? If so, that is the complete opposite of the Meade setup, and I greatly apologize for misleading you.

    Derek


  3. From the position that my OTA is in, if I tilt it straight pack so that it is in line / parallel to the fork arms, then it is pointing at Polaris in the polar home position. But I never used Polaris to polar align with my setup (view was blocked). I always drift aligned.

     

    Derek


  4. If you tilted the OPs scope to point at NCP in the current configuration , the top of the OTA / finder scope would still be on top. Nearly every SCT on wedge I’ve ever seen is rotated 180 degrees. With the forks in that position, you may never be able to get close to zenith as the imaging train could collide with the fork base. So the fork arms need to be rotated 180 degrees. Why would it be any different Meade vs Celestron?

    https://www.telescopesplus.com/products/celestron-9-25-inch-cpc-deluxe-hd-eq-wedge-telescope

    Derek

    B3458BF8-9CC0-43D6-BE9A-7AF04F7907E2.jpeg


  5. Did you loosen the (three?) nuts that secure the base of the wedge to the tripod before rotating the Az wheels? It won’t move if you don’t. The movement is fairly minimal/fine with each crank of the wheel, so it might not be very noticeable at first. 

     

    Derek

     


  6. With respect to the M Uno and periodic error, I have well documented the large PE on my M Uno. But to be clear, unless you plan to do unguided imaging it has absolute no effect on the resulting images or FWHMs. I think that Avalon should make it more clear on their websites  that these belt driven mounts with multi stage reductions are unique, and while they do indeed have very large periodic error, it is so slow and smooth that it is inconsequential when guiding. I have taken single sub exposures of two hours duration at a focal length of 2350mm with guiding < 0.5" total RMS, with resulting round / tight stars with FWHM < 2".

    So I think Avalon mounts redefine the concept of periodic error, i.e.: it doesn't matter. And those that criticize the mount because of the PE have probably never used one. They are simplicity defined. No flip, no maintenance, no worries.

    Derek

    • Like 1
    • Thanks 2

  7. If it points in a completely different direction than expected, go into the advanced panel in StarGo and try checking the "reverse motors dir" boxes one at a time and retrying. I had the same problem on my Uno and have to check the "dec" box.

     

    Derek


  8. I just recently started dithering after many years of imaging, and can say without question that my images are far cleaner than before. I now rarely  need to use noise reduction and can even get away without dark frames. I may have gotten lucky with my dither settings, software (APT/PHD) and backlash free mount (M Uno), but my time between dithered  sub-exposures is never more tha 10-15 seconds. It was far longer and inconsistent before I switched from SGP to APT for what it's worth.

     

    Derek

    • Like 2

  9. I just got APT and really like it. I have had SGP for a while, and while most rave about it, I found it to be less than user friendly. I find APT to be easier to navigate. APT doesn!t appear to have automated meridian flip or allow for unattended automatic focusing which SGP does. But my mount doesn't require a flip, and I focus well enough with just temperature compensation with my Optec TCF-SI on both my refractor and SCT.

    Derek


  10. 3 hours ago, frugal said:

    I have to say, for all that people rave over the Avalon mount, I was expecting a flatter guide trace than that. I can regularly get 0.8" RMS guide error on my AZ EQ6GT with poor polar alignment. 

    A guide trace is just that and nothing more. I think we rely too much on numbers. There are many other mount related issues that affect the end result. The FWHM and eccentricity of your stars in your subs are what really matters. Like I said, these mounts are unique and numbers used to compare other mounts IMO don't apply here. Again, while I often get < 0.4" total RMS, even when my guide trace looks like a polygraph with RMS well over 1" the stars are still impossible round and tight. I think I remember Olly suggesting it here, that the the belts promote such rapid response to guide pulses, that perhaps the star spends more time on pixel. I've seen folks with superb guide numbers on different mounts that still have fat egg shaped stars. I've not had a fat egg shaped star in two years.

    Derek

    • Like 1

  11. I have been assessing my unguided periodic error and RA drift on my Avalon M Uno. In fact they are ridiculously large. I have no idea where the +/- 7 arc-sec figure comes from. The periodic error on my mount over the 4 stage belt/pulley reduction is somewhere in the 40-50" total range. But these mounts are unique. IMO, periodic error is meaningless with these mounts.  Yes, they must be guided, but they guide superbly, perhaps better than any other. On nights of good seeing, my total RMS guide error is <0.4" and I have taken 2 hour long subs with resulting FWHM of <2" at focal length of 2350mm. I was more concerned about the RA drift because of the possibility of losing a guide star during prolonged periods of cloud cover. But the newest StarGo firmware addresses this with a real time automated RA tracking adjustment based on guide pulses.

    Regarding the elasticity / wind issue, does anyone (Beeko?) know what was actually done to address this, and is it an adjustment available to owners of older mounts?

    Derek


  12. On March 15, 2017 at 09:54, Tommohawk said:

    Thanks for all the helpful responses. I guess I was interested partly from the theoretical, but mostly from the practical viewpoint, particularly when comparing refractors with reflectors.

     

    This is purely a practical comparison but gets to the point. The first LRGB image is a crop of a wider field around M106 taken with a 90mm f/7 APO refractor. It was rescaled to match that of the 2nd image which is a mixed focal length shot using luminance from a 10" f/10 SCT, superimposed on the refractor image. They were taken with the same CCD on successive evenings under similar sky and seeing conditions.

     

    Derek

    image.jpg

    image.jpg

    • Like 1

  13. I use only PS. I've thought about trying PI, but I really don't believe that my images will improve significantly, nor that there is anything that I can't do in PS that I would be able to do in PI (other than stacking). Also, it seems to me that while many use PS exclusively, few use PI exclusively and why use two programs if not essential. of course this is a biased opinion because I've never used PI. I've always thought an interesting challenge would be to post calibrated stacked subs of less than optimal data of a challenging target, for anonymous users to process exclusively in either PI or PS, with judging of the results by individuals blinded as to which program was used.

    Derek


  14. On January 9, 2017 at 09:11, Zakalwe said:

    Probably because very very few people would use a fork mounted system for imaging.

    Actually there are a lot of people who image successfully with fork / wedge mounted SCTs despite the challenges. And the Avalon M Uno and Zero are single arm equatorial forks. A simple universal dovetail mount for the PM would work well for these.

    Derek

     


  15. On January 8, 2017 at 14:43, Ford295 said:

    Hi Derek,

    Just a quick question about your fitting. As it attaches to the OTA how do you setup the OTA in the forks? Do you achieve 90 degrees pointing north. When I use mine, I go through the process apparently successfully, but PHD2 reports a really bad drift. If I then adjust the drift to bring alignment back, Polemaster shows it as being off. I am thinking it must be the way I set the scope up. I normally  get the tube to about 88 degrees and Polemaster shows Polaris on screen and as I said every thing seems to go well. 

    Any advise would be great.

    Kevin

    Hi Kevin. Yes, I have no problems getting to 90 degrees dec because my mount is a single arm equatorial fork, si I have no issues with the CCD contacting the fork base. i suspect that this may be the related to your problem. Though the pokemaster works fine off axis, I suspect the software assumes that your mount is in a home/90 position.

    Derek

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