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About Johanvk

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    Photometry, Astrometry, Spectroscopy, Astrophotography variable objects.
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  1. Thank you. It is informative and systematic, and it lead to other relevant sources.
  2. I moved from color (Canon) DSLR camera's to more advanced ZWO black and white camera's with color filters. Now I have to handle gain and offset instead of ISO. In theory I think I understand very well what it's about, and took notice of the literature. In practice at the telescope I have to rely on trial and error with test exposures. Can someone point a (reference to a) cookbook-like procedure to me, which lead to the optimal setting of gain and offset? Johan, Netherlands. [C14/Hyperstar, with a ZWO-183, and with a lot of light pollution.]
  3. I tested the StarAid. An interesting development, but be aware it's in the beta-test phase. Ask quantitive specs and proof before buying. It's not cheap.
  4. These flats pose an urgent problem for Hyperstar. Since two years I operate a(n older) C14 with a Hyperstar, and spend quite some observing time last year, on getting decent flats. All customary advice (T-shirt, domeflat, lightbox, flatscreen, etc.) did not work. The only reasonable results were obtained by sky-flats. But the timeslot to get them is only about a quater of an hour in twilight. Otherwise the image is either saturated or too many stars turn up (at the F2). I don't understand why this is not reported wider. Either I'm missing something, or I'm clumsy. As it stands I suspect de F2 bundle catches too much internal reflections to allow the usual flats to be taken. The speed of the Hyperstar is a great advantage for me. The flats however limit photometric use and mosaiking. I'm stuck - please comment!
  5. I'm since a few months experimenting with an Hyperstar on (an orange) C14 with a Losmandy mount. So far it looks promising. The reason to go for an F2 system is that we already have good greater F-ratio telescopes on site. Also an OAG was almost impossible to use, because finding suitable guiding stars was a (wasteful) time consuming, and frustrating, job. A more expensive guider camera was not in the budget. The speed is indeed amazing, which is important considering the small amount of clear nights here. Autoguiding is done with a guiderscope, but I want to see if that is really needed at all, with such a short focal length, and such short exposure times of subs. The chip of a DSLR can be covered rather well (using flats etc.). The reported problems with the very small focussing range were not encountered - just turn the knob. A limitation is posed by the pixel size of 1.3". I'm not sure what the effect of tha limitation is on the sort of photometry I want do do. So far I did not test (narrow band) imaging through filters. On any bigger telescope these become exponentially more expensive... Testing is still going on. For a (more modern) Edge I would certainly consider an Hyperstar, especially because the F2-F10 set-up can be switched so easy.
  6. Thank you very much for your offer, but I gave up. After contacting Perry from WillBell, AIP4WIN was downloaded and completely reinstalled, according to his instructions. Both on the original PC and a new one. No success. After that I did not get any further response from Perry. To me it seems this software is at the end of its life cycle. Spending more time on this product is not worth while. So I replaced it by AstroimageJ which runs flawless and fully fulfills my photometric needs.
  7. AIP4WIN, which I used for photometry, does not run under Windows 10. The supplier gives some polite answers but leaves is there. I switched to another program which performs satisfactory. The book is good, but I removed the AIP4WIN-prgram as being unsupported software. (All my other software transported from Windiows 7->10, run smooth, and to my surprise often faster.)
  8. I had to transport AIP4WIN from Windows 7 tot Windows 10. The installation and registration looked good. But the program does not start, in administrators mode only a "missing file" message pops up, further nothing else. The author responds but is not helpful. Has anyone encountered this problem (and solved it)? I use this program to my satisfaction for stellar photometry. If this installation gives so much hassle (now and thus probably in the future), what are the alternatives? If available, I do not want to install another heavy image processing program, just for the single application of stellar astronomy.
  9. I had something similar when I interchanged (by accident) the RA and Declination connections, so PHD moved the wrong axis. Keep this confidential please...
  10. I'm pretty sure this artefact is a result from the algorithm of the stacking program. Registax sometimes did the same for planets (bright objects in dark sky). The registration points devide the image with tessation and fit the aprts on the individual (AVI) images. With a few alignmentpoints the tesselation bounderies sometimes show, becaues of the small adjustments arount points. By choosing more or other registration points it disappears. As a matter of fact, for planets, just choosing only 1 algnmetpoint in the middle in a contrasted area is sufficient. Differential seeing does not distort that much across a planetary disk. NB.: I had to check the value of £3 in € - boy, this image is an enormous value for money!
  11. For the final focussing I always use (a serie of) short exposures of some brighter stars in the field (or nearby). Visually judging the zoomed in stellar images and turning the focus knob in small steps. It takes only a few minutes. The digital and optical help ofter apeared, later on, not to be perfect. And it is a disappointment when focus appeared not to be perfect after a long night of imaging.
  12. Just for the census: I am a reasonable happy user of GIMP for processing DSS and Registax images. Only for producing nice color images Photoshop output looked a bit better. But I cannot afford much commercial software.
  13. Hi, Not too bad for 17 minutes. What I would try to improve: - It seems there is strong vigneting. The corners look very dimmed. For a huge object like M31 this distorts the intensity and the looks of the image. Also Photoshop-like programs do'nt like this (especially 8-bit GIMP). Firstly, this is what you get when using a DSLR with a 1.25" connector to the telescope. A 2" connector is a must. I do'nt know what you have. Secondly, it looks like no flats are (effectively) applied, this would bring a big emprovement. Flats are easy to make and applied (like e.g. DeepSkyStacker does). - If your polar alignment is reasonably good, exposure times of 1 minute must be bearable. (Now it looks like there is a slight field rotation). The galactic center is bright compared tot the arms, but (besides some globular clusters) contains not much detail. Some image processing is needed to get center and disk with acceptable contast in the same picture. Fun to get these things done, is'nt it? Regarda. Johan.
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