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  2. @RolandKol Speaking about focus. I got my ASI1600 today. And there is talk about this 55mm backfocus, which i dont understand. 55mm from what? I see from the picture of your setup that you have an OAG on. I dont. How would i attach all these rings in the focuser to get the correct "backfocus" ? I saw some drawings on ZWO homepage, but i dont get what is left in the focuser? Do i take away that adaptor which i had to loose and had to tighten which I mentioned earlier in the post, or what do i do?
  3. Since starting this thread, each of these eyepieces has become available secondhand. The Panatopic sold for £300 and was too expensive for me. The Vixen LVW went at a bargain price of £100 and I was simply beaten to it by another lucky member. This week, I picked up a 40mm Aero for a total price of £49. I was encouraged by Michael and John's words of praise for this eyepiece. It arrived today and skies were clear so it got a quick first light run out. Report here for those that are interested:
  4. Chris, Not exactly the same, but I have manged to record down to 3700A with a ATiK314L+ with the slit spectroscope. Without a UV cut it really depends on the optics and camera response. I'm interested to hear about your objective prism....I have a 20 deg f2 prism which can be mounted in front of my ED80.... early results with a FULL modded DSLR were very promising ( especially in the NIR) Ken
  5. Yes, I see it with my ST102 as well. For some reason it seemed even worse on the ST120. James
  6. Weather and tiredness have pushed astronomy to the side for me recently. The last two nights I put the dob outside to cool and was then too tired to do any observing. The arrival of a new eyepiece today gave me the extra little push I needed. I've been looking for something in 40mm focal length region and decided to go for a 40mm Aero, which came up secondhand this week for a shade under £50. With my Equinox 80 refractor it gives 12.5x magnification and a huge 5.4 degrees TFOV. My skies at home are around 5 - 5.5 NELM so I wasn't too sure how well the 6.4mm exit pupil was going to work. I started in Cassiopeia, using the red dot finder to align on Ruchbah. The hazy glow of NGC663 was immediately obvious and I soon realised that I had a clear view of M103 too. I have 10x50 binoculars and the views were not dissimilar. It was much nicer with the steady view through the refractor and without my arms getting tired from holding the binoculars. Panning over, I next found the delightful NGC457. From there I went to the double cluster in Perseus. Whilst the lower power widefield lost much of the detail I'm used to in the dob, it added so much context to the view. I really enjoyed seeing the way these clusters fitted in the wider star fields. Nothing exemplified this better than Kemble's Cascade. The fine chain of stairs sparkling all the way down to the tiny cluster, NGC1502. Open clusters were a winner but what about galaxies? Andromeda was the obvious first choice and the bright core showed well. With some careful study and verification with SkySafari, I also picked up M32. I looked for M110 but I didn't see anything definite for this. I felt very confident that this would show well at my dark site though. Over to Ursa Major and the pairing of M81 and M82. Bode's showed quite well straight away but the Cigar took more patience. Averted vision was able to bring out the side on galaxy. The Moon was rising so I looked for areas of the sky that weren't yet showing signs of Moon glow. In Lyra, I place Sheliak and Sulafat in the centre of the eyepiece. I thought I was pushing my luck trying for M57 but there was a distinctly fuzzy looking star in the right place. SkySafari was again used to confirm the observation. The Ring became the first planetary nebula of the night. I screwed in the Lumicon OIII filter and moved over to Cygnus. The faint Eastern Veil was the first thing to catch my eye, soon followed by the Western Veil. Both faint but clear with direct vision, comfortably sitting in the same field of view. The North American Nebula, required a bit of time to become clear. Over the course of 5 minutes it noticeably gained in prominence as my eyes adapted to the view. I took a punt at moving over to the Crescent nebula. A nebulous glow grabbed my attention straight away. SkySafari proving that my eye had successfully detected the nebula. With the OIII filter now removed, I gave a little chuckle of delight as I looked upon the pinpoint stars of M29. There was something so lovely about recognising the little cluster. The larger cluster of M39 was like an arrow head within the larger star field of the Milky Way. Albireo was quite a close double star at 12.5x mag and every bit as pretty. The coathanger hung in the sky and made a fun diversion on the way to finding M27. The dumbbell was easy to spot. My evening drew to a close with an averted vision observation of M71. It was fun to be eeking out views of these bright Messiers at low power. Normally easy targets made challenging. All in all, I'm very please with the 40mm Aero. It's a great pairing with my refractor and really opened up the skies for some fun and engaging observing. 21 objects observed in just under an hour. If I'd lost any enthusiasm for stargazing these past couple of weeks then it's now been fully restored!
  7. The great thing about the wedge, as you know, is I can drop it down into Alt-Az at any time I was looking at a faster scope as well. I just got mmy 6SE yesterday and what A BLAST! Well I won't hijack this thread, so hopefully soon I can post something DSO. I was able to test my 450D last night and got a few 20 sec exposures of the Andromeda Galaxy. I am now cramming knowledge so I can get this whole post-processing figured out. Thanks1
  8. Follow-up: I discovered play on the RA axis and a lot of backlash on the mount, which I set out to fix. Sadly, I got a vout of kidneys stones that have taken 4 weeks to get sorted. The RA play has been sorted by careful adjustment of the wormgear hex screws and I've also replaced the cgem saddle with the human friendly one from ATM. I've now got a very smoothly balanced mount with a much easier means of balancing the OTA. Only the weather is standing between my setup and the next picture.
  9. I think it is better to look at it this way: CCD camera with 5e read noise and certain pixel size - let it be for example 4um, with hardware binning - produces effectively camera that has 5e read noise and 8um pixel size. CMOS camera with 2e read noise and certain pixel size - let it be the same as above 4um, with software binning - produces effectively camera that has 4e read noise and 8um pixel size. Regardless of the resulting read noise - one can deal with it by increasing single exposure duration (less subs for same total imaging time) - as it again adds like you said when stacking subs, and by increasing sub length you can make it be much less than other noise sources (a bit harder for narrow band but doable).
  10. Rolling shutters are a feature of interline type sensors, and shutters are used for full frame transfer sensors. Its all about the speed of which the image is read from the sensor (interline = fast, full frame = slow) http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_07.html http://www.optique-ingenieur.org/en/courses/OPI_ang_M05_C06/co/Contenu_09.html
  11. You can't just guess the spacers needed, you have to measure. Measure 200mm back from the objective. Measure how far inside the camera the sensor is. With the focuser in midpoint of travel, mount the camera so that the sensor is at the 200mm point. Fine adjust focus with the focuser. Michael
  12. Many thanks for these very useful replies. The camera (Nikon D750) is un-modded so does have a UV/IR cut off unfortunately, but my AS1224 (colour) doesn't seem to go much lower in wavelength even without one. The reason I need to go down a bit more (apart from the interesting spectral lines below 400 nm!) is because I'm using an objective prism and need the 410 nm H line if possible as one of the three lines I've been using to linearize the spectrum from the prism using the BASS software. The prism is mounted in front of an ED80 (fl 600 mm) which is close to the fl of the original lens in the Hilger 0.5 m spectrograph that the prism came from. That went down to about 320 nm or so, but using film rather than a sensor of course. In the blue part of the spectrum, the objective prism is giving me a resolution of about 3 - 4 times better than I get with the SA100 I have. Chris
  13. Sorry - yes, I hadn't put it well - I meant CCD binning only works in comparison to CMOS when read limited. If you aren't read dominated then the SNR doesn't increase by factor 4 (but yes, the other noise terms add in quadrature). It is important to state which realm you're working under - if you're dominated by read noise, the R squared term in the ccd equation dominates (and leads to the 4x reduction for ccds, but 2x for CMOS). You have to cope with the corresponding loss of resolution though.
  14. @Graeme, many thanks for the picture and apologies as well for the time it took to respond. I've been out of action due to kidney stones, which I'm not going to go into here. I don't remember where now, but I did find info on where the FR was supposed to go in the first place. In front of the camera, as you say, and further away if one want a different FR ratio. I've been having tracking issues, which I've tracked down to a loose RA axis and which resulted in horrible backlash. Rather than attempting to compensate for that I decided to adjust the worm gears. I now have a very smoothly balanced and backlash-less mount. I also changed the saddle for the ATM one, which is very forgiving when balancing and has human friendly knobs. The original celestron cgem saddle is not designed for people with long hands and fingers, like me, and is in fact a bit dangerous. My next challenge is to fit a 2"filter to the OT. Many thanks for your support!!! R:)
  15. Today
  16. Normally using pixel math in pixinsight i dont have any issues combining rgb with ha but on this occasion its not working as well as i would like. Ive followed the procedure as normal from the light vortex tutorial but still not great. Any guidance would be really appreciated. Thanks Ken Both images are stacked and have had background extracted but no processing. HA https://drive.google.com/file/d/1z5Ufk2hq4QdP2TgYl-wBSCcCSquaGJqD/view?usp=sharing RGB https://drive.google.com/file/d/1OUOwLHKNG8apvbVV4fCqx2jaDuuu_Dca/view?usp=sharing
  17. Focal ratio is governed by focal length divided by aperture end of.. so that's why f5 scopes don't have the same fov if either the fl or the aperture is different.. focal length gives you big the target will be, the aperture gives you the brightness as more photons are captured, if your imaging circle is bigger it can illuminate a bigger sensor.. Thought it was about microlensing anyway
  18. I do. I owned ST102 - that is 102mm F/5 scope and chromatic aberration was horrible on bright targets, but that is not what the scope was intended for - it is wide field scope. I sold that one and got Evostar 102 F/10. Yes, it does have blue fringing, but I found that Baader Contrast Booster helps a lot with that. Moon is almost clear of CA with it and still has rather neutral tone. I briefly observed Jupiter with it on one occasion and again there was no bright purple halo with this filter. You can use wratten #8 yellow as cheaper alternative but it will give you slight yellow cast on the image. What you can further do to reduce chromatic aberration is to use aperture mask. It reduces aperture and increases F/ratio at the same time. It will limit max usable magnification, but will provide much clearer image. For example using 80mm aperture mask, you will get F/12.5 scope. If you look at above posted table - you are in the green zone and still have a scope capable of delivering around x160 magnification. I'm sorry but that simply won't work. You can image with such scope though and get some decent results. You don't even need mono camera for that. There are couple of tricks that you need to employ in order to minimize chromatic aberration issues (one of problems is that you will no longer have F/5 scope, but that does not matter - it is aperture at resolution that determines the speed of the system). Here is an example: First ST102 F/5 scope without any "tweaking": Image is rather poor as it was one of my first attempts with OSC camera (small sensor) and this scope. Camera had no cooling and it was QHY5IILc I believe - so not a very good camera. But that is not the point - resolution is terrible because of CA issues and there is large blue bloat around the stars (and red around smaller stars). Now here is the image done with the same scope and different OSC camera - but not too different. Still 3.75um pixel size, still uncooled - it is ASI185. And later same target, a bit smaller field but better color correction: As you see - no fringing and images are quite "decent". Trick is to use aperture mask (66mm) and wratten #8 filter - or that is what I used. No special processing was done to remove bloat from the stars.
  19. Thats why forums like SGL can bs so useful - just keep asking the questions, there is a heck of a lot of experience on here
  20. A 4 inch achromat has to have a focal ratio of F/15 or so to show no false colour visually. At around F/10 the amount of false colour is really quite small so that is a popular focal ratio because the scope tube is manageable (ie: not too long). The achromats that operate at F/5 or F/6 do show quite a bit of false colour but their main intended use is for low to medium power viewing of deep sky objects and in this they do a good job. There are filters that reduce the amount of false colour that is visible but they do tend to add a noticable tint to the image. Some people find them useful and some don't like them. A 8 inch F/6 newtonian will show no false colour at all and is likely to show excellent planetary views.
  21. It's a clear moonlit sky here currently and been thus for the past couple of hours, however, I haven't been able to use it.... Firstly I got my main imaging laptop back from the IT guy who was able to bring it back to life sufficient to recover the data, but he advised that the machine itself, whilst currently working, is really for the scrap heap, so I took his advice and have ordered a new replacement. I spent much of the rest of today getting all the data and various program installers off the laptop to external hard drives ready to set up the new laptop when it arrives.... Secondly about 2 hours ago I thought I'd head out to the obs and try some new adaptors to connect my QSI camera to my 4" TSAPO. Currently I have to take the camera down and change the face plate between a standard 2" T-mount and a wider USA 2.156" mounting when switching between the C14 and 4" APO. Last week I purchased a 2.156" x 2" nose for the QSI to make the switch straightforward, so I was hoping to use that tonight, BUT as I now find that there is insufficient travel in the 4" APO focus tube to get sufficient back focus for the camera and after rummaging through all my various fittings and adaptors I don't have anything make up the difference. What I have is either too short or too long, so I have just ordered something in between - hopefully next time, I'll have what I need.... Thirdly, frustration and generally tiredness got the better of me, so I shut everything down and came back indoors. Sorry for the long moan, I will have an early night instead
  22. Here some info and what to use : https://starizona.com/hyperstar/ Also there are videos on YouTube for other explainations :
  23. I have no experience but I’ve been researching Starizona Hyperstar recently as I plan to buy it too. See links below https://www.astroshop.eu/hyperstar-faststar/starizona-hyperstar-fuer-celestron-c8-v4-mit-filterschublade/p,62680?utm_medium=cpc&utm_term=62680&utm_campaign=1910&utm_source=froogle&gclid=EAIaIQobChMIsrSSo6Wk5QIVgrHtCh3AHw7REAQYASABEgIZLfD_BwE&utm_content= https://www.rothervalleyoptics.co.uk/search/for/Hyperstar+c8/ Also a few good videos on YouTube. Ben
  24. Nice review Chris, that gives a really good feel for what this setup is all about. At £175 that's terrific value IMO. A couple of questions: (1) Does the mount have a standard tripod fitting (3/8"?) and (2) do you think a sturdy camera tripod, like the Horizon, would be any better, or does it need something like a 1.75" leg tripod? Love the beard by the way!
  25. How do you equalise a subtle gradient (especially in one colour) from left to right Olly? What tool or method would you use pls?
  26. Thanks for doing the maths John. It does rather put it into perspective.
  27. Hi Ruzeen, welcome to SGL
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