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About alan4908

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    Star Forming
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    Astrophotography ! the moment I'm concentrating on deep space imaging
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    East Sussex

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  1. I noticed that the Ascom installer for 6.3 has been recently changed to fix a leap second issue ( Does anyone happen to know what the impact of this bug was on the accuracy of platesolving, pointing etc ? Alan
  2. Hi Chris Thanks for the clarifications. Since, I have developed the habit of reflecting back (to check my understanding) On the orthogonality error - with my latest model I have 21 terms, so the two sides of the meridian are being modeled separately. I'm still not clear if you are saying that reducing my orthogonality error will improve my tracking or simply that this will improve my pointing accuracy or it will improve both tracking and pointing. The user manual states "In order to obtain optimal performance, it is not required to correct physically the orthogonality error". It also states that "It is not necessary to correct physically the orthogonality error in order to obtain a good pointing accuracy or tracking". On where to synch align - if I wish to resynch then you are suggesting synch aligning at a point where the plate solving would be most accurate eg somewhere near DEC 0, rather than where the where the model errors (visible in the model graph report) are the lowest. I'm still waiting for my mbox, it's good to see that it is working for you ! Alan
  3. Feel free to post the leaflet anywhere you want since it's public information (it's only recently been completed by Baader). Unfortunately, I don't have any comparisons with dual axis enabled versus disabled during model building. With dual axis disabled, my model was 97 points at an 2.82 rms with 21 model terms. Thanks - this is mainly due your suggestion of covering the sky with more points. Your error is impressively low, I believe my orthogonality error should only impact pointing rather than tracking. Currently I instruct ACP to correct any pointing errors larger than 0.15 arc mins, by doing an autocenter without issuing a synch align, so I don't think this is something I need to test, however, correct me if you disagree ! Chris - just to make sure that I understand your ecliptic comment correctly. I think you are saying that the lower the DEC of the object the more difficult it will be to guide. Since I like formulas to describe things, I found this one from Chris Woodhouse's book "The Astrophography Manual" page 279: Autoguider rate = 15.04 x guide rate x cos (DEC)/autoguider resolution (arcsec/pixel). Since I'm not autoguiding, I presume I can modify the formula so: set the guide rate = 1 and the autoguider resolution will be my main camera resolution. So, the rate that the unguided mount will need to correct things will be determined by: Mount correction rate = 15.04 x cos (DEC)/image resolution (arcsec/pix). So, the lower the DEC angle or the smaller the image scale, the higher the correction rate, is this what you mean ? Chris - just checking that I understand this - I presume this is test for orthogonality error rather than tracking. Is this correct ? (see also my comment above) Anyway, since it was partially clear last night, I decided to have another go at some more 1 hour subs, again only using my 3nm H filter. Again, I decided to only let ACP perform an initial synch align after it had performed the first autofocus of the evening. I only got three subs before the clouds rolled in and my observatory decided it had enough for the evening. M81 - 3600s H uncalibrated (DEC:69 degrees, Elevation at Exposure start: 69 degrees) M66 - 3600s H uncalibrated (DEC:13 degrees, Elevation at start of exposure: 46 degrees) NGC4631 - 3600s H uncalibrated (DEC: 33 degrees, Elevation at start of exposure: 60 degrees) When I put these through CCD Inspector I get average Aspect Ratios of M81: 23; NGC4631: 9; M66:65. Clearly M66 is bin material and the formula above predicts that this would be most difficult to image. What's interesting with the M81 sub is that when I look at the stars in the centre of the image with MaximDL's Information window, it is telling me that quite a few of the stars near the center have much smaller aspect ratios, maybe CCDI is getting a bit confused over the H regions which are quite bright. I'm still intrigued to understand if the point where the initial synch align is performed has a subsequent impact on the tracking performance. Since the model error is not uniform in all directions (eg in my case an RMS 2.82 arc seconds is predicted), intuitively, I would have thought that it would matter. If this is correct, then presumably the optimum place to perform the synch align would be at that region of the model which has the lowest collection of pointing errors ? Any thoughts would be appreciated ! Alan
  4. I managed to get a few subs with the new sky model I built with dual tracking switched off. This takes onboard Barry's suggestion of increasing the number of points in the skymodel to over 90 and covering all the sky that I would be imaging. The synch align issues which I was previously experiencing appear to have disappeared with everything now apparently working with just one initial synch align with ACP. Although the night was a bit cloudy, I decided to try out a one hour single exposure on M106. To ensure that the stars did not become bloated I used my 3mn Ha filter. CCDInspector reports that the average star aspect ratio is 10, the uncalibrated result is below. So, it all looks very promising, all I need now is a few more clear nights to confirm everything is OK Alan M106: 3600s single sub unguided - 3nm Ha
  5. Yes the comment from Baader on dual tracking is a little strange. Since Baader are a respected company, my working assumption is that it will improve matters, but probably by only a small amount. Baader have now produced a document which clearly states this which I attach for your information. It is encouraging to see the synch aligns working for you, Barry. If I've understood the purpose of the synch align correctly, I cannot see the disadvantage of performing this after each image acquisition. I have just (whilst typing this ) created a 97 point model (with dual tracking off ) and deleted 3 outlying points, 2 off which where associated with the 3 base points. I'm following all your other points with the exception of the orthogonality error (which is currently estimated at 13 arc minutes with my new model). I haven't yet received my mbox yet, so I'm having to enter temperatures manually to compensate for refraction effects. I may well take you on your offer as a sounding board via PM.....I'll first see what the results are like with my new model. Alan EN_HPS_quickstart-manual_A5_RGB_LR_0317-3.pdf
  6. I've had my NEQ6 since I started astrophotography 3 years ago and overall I've been very impressed with its performance and particularly its ability to be integrated into my ACP controlled, automated imaging observatory set up. Since the UK has relatively few clear nights, I decided to purchase a new mount that would (hopefully) increase my DSO acquisition efficiency. I also wanted a mount that would also allow a heavier imaging payload since I was also planning to acquire a long focal length APO refactor to complement my existing SW 80 ED. In selecting a new mount, I decided to look through my ACP logs where I discovered that that guiding errors where my number one cause of lost subs. I also noticed that it took ACP quite a time to acquire a suitable guide star, wait for the guider to settle and actually begin guiding. Very occasionally, I had also experienced the mount losing its park position when powered up. Since my telescope can hit the observatory roof this was somewhat alarming and so I always made sure that I was physically present whenever powering up the mount. After taking into consideration all of the above, I decided to buy a 10micron GM1000HPS, mainly because of its ability to acquire long exposure unguided subs. I also liked the fact that it had absolute encoders and so, should always know its relative sky position. The tracking of the 10micron mount is based on the principals of telescope pointing by Patrick Wallace ( with 10micron having developed a proprietary algorithm for solving the various equations that model the telescope. The first thing that I discovered is that unlike a normal equatorial mount, you can obtain much better results if your pier is level rather than approximately level. I also discovered that tracking could be further improved if you had quite an accurate polar alignment. By contrast, tracking appears relatively insensitive to orthogonality error. For those that might be interested I eventually settled on a polar alignment error of 43 arc seconds and an orthogonality error of just over 16 arc minutes. To solve the various equations that allow the telescope to point and accurately track you have to build a sky model, you can either do this manually or automatically using various sky model making software options. Having chosen to go down the automated route with Per's Model Maker, I eventually built a model with 41 points and achieved a RMS of 2 arc seconds having deleted two outlying points. In the course of my various attempts at model building, I noticed that the placement of the first three points (base points) is critical. These need to be equally spaced, cover both sides of the meridian and vary slightly in altitude (I choose around 50 degrees). I also discovered that I could get a lower final RMS if I modeled the two half's of the meridian separately with the refinement points. I presume this because the mount is slewing less and hence introducing less random errors. I currently plan to pursue two issues: 1. When the mount tracks across the sky, it does so in both RA and DEC - 10micron call this dual tracking. What is confusing is that the user manual implies that the dual tracking should be on during the making of the sky model, so lots of people over the years appear to have built models with the dual tracking on. Baader Planetarium (the European 10micron distributor) has recently stated that dual tracking needs to be off during model building or polar alignment. I'd therefore be interested to know from anyone or has done a comparison test between the two approaches. 2. After you've built a model and want to come back to it several days later and nothing has changed - you are only supposed to perform one synch align (which apparently sets the encoder offsets). I've tried this in ACP and I obtain very poor results. However, if I resynch after each acquired image I get very good results apart from the first image which has elongated stars. I have a theory that where you choose to perform the synch align is critical and is dependent on the model you have built. Anyway, I'd be interested to hear from anyone who has managed to get this to work. So, having built the sky model, I decided to try it out. Rather than focusing on random objects, I decided to pick NGC2276 mainly because it was always visible from my location at this time of the year and also because it was well above 30 degrees altitude, hence refraction effects would be minimized. My initial test LRGB result is below which consists of 10min subs, the vast majority of which have aspect ratios of between 4 and 12 (as measured by CCD Inspector), my quality threshold is 15, so I'm very pleased with my first attempt at unguided imaging. Alan
  7. Pieter - thanks ! In addition to the Photoshop's High Pass Filter and Unsharp Mask, this time I applied Pixinsight's HDRMT routine, which is excellent at sharpening images. Alan
  8. Great image Herra, I do like that field of view ! On the airport subject, although I'm fortunate to have relatively dark skies, planes are probably my major source of artificial light pollution. However, they don't really cause an issue for imaging since the resultant pixels lines easily get rejected without a trace with my stacking software. Alan
  9. Thanks for the comment Olly. In terms of the addition, yes - I was actually thinking of adding some OIII data at some point since I think it would improve the overall effect. My only issue at the moment is the UK weather ! Alan
  10. Thanks Paddy !
  11. Thanks for all your comments. It was quite an interesting object to process since the nebula is very faint in Lum but you have a very bright star next to it. Alan
  12. From the album Deep Sky II

    This is an LRGB image with Ha blended in the Lum and Red channels. The Lum was quite faint, even after over 3hours, so I decided to blend quite a large amount of Ha in order make the image reasonably bright and not too red. The Ha is also blended into the Red channel but at a much lower level. I made a slight change to the Hue, towards the green, in order to get a slightly more appealing red. In total, the image represents about 13 hours integration time.
  13. Thanks Paddy.
  14. Thanks Dave - yes, the combination of poor weather and a restricted horizon does make it frustrating ! Alan
  15. Thanks Olly - I think the reprocess was worth it !