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  2. None. 1/10th wave is not that great, modern apos have 1/20th or 1/30th wavefronts, sometimes better, and given that the average visible wavelength is 0.5 micron, 1/10th wave is 0.05 micron. But a 130mm Vixen doublet apo tested 1/60th wave in Rohr's lab, and a TeleVue diagonal tested 1/85th wave. The crests and hills in the glass were only a few dozen molecules across. The current standard for high-grade scientific (and military, I suppose) optics is 1/100th wave, and is obtained by milliing the surface with an abrasive ion beam after all the bumps and pits in the glass have been mapped by a computer. A very accurate arm moves the beam across the surface and shoots ions were the bumps are know to be. Only one amateur I know of has his reflector rectified to that standard, Tony Hallas if I remember well. It must have costed him a fortune.
  3. I have available for sale a Skywatcher 150 pds photographic Newtonian reflector in very good condition. It has the 9 x 50 finder upgrade, tube rings & a dovetail fitted. The mirror coatings are in very good order. I am looking for £120.00 postage paid or collection from Redhill, Surrey. I can supply a detailed set of photos on request.
  4. Hi is this mount still for sale.
  5. Am I right in thinking the 150pl has a better magnification and can see further and more detail of planets and the moon
  6. The minimum number of exposures to do it right is about 2000....how much storage space / time to stack 2000 x 16mp images? 5 seconds or less exposures at very high gain is where you want to be. I believe something like 64GB of data. The advantage of the smaller camera is that you can actually stack it in less than 48 hours lol. The other issue is read time, you will lose a significant amount of time reading the data from the camera between exposures.
  7. Interesting thought! I've not been in this game long enough to worry about x2, x3 etc and loss of detail. I've alway just shot full resolution with my ASI1600MM-pro-cool as I read that the binning is in software. If I use the camera in full rez mode then later downsample in post processing, would I still get the same benefit? and if so, when is the best time in the process to downsample (eg, before integration, after stretching etc etc?
  8. Chris, currently I'm observing because I'm learning the proper techniques of the mount and telescope, but in the very near future (I hope) to start imaging. I currently am using my Canon DSLR 70D but am considering on purchasing a dedicated imaging camera. I'm looking at the Orion Star Shooter G4 camera as a purchase. Thank you for your input.
  9. Yes, I did wonder about this some time ago - why is there such discrepancy in different measurement methods - and this article shows that discrepancy is real and even increased.
  10. The first part of the job is indeed automatic (not necessarily computerized) but the required accuracy is too fine to be obtained like that, the surface has to be analysed and improved. So it is inspected by a person, refined, re-inspected and so on until it reaches the standards. Remember that a high-end apo of only 100mm must stand 300x and remain sharp and contrasty, so imagine how the six surfaces of the three lenses must be smooth and perfectly curved to transmit a sharp image that can be enlarged 300 times and show no defects. Just look through a regular window at low power, only 40x or so, the image will be blurred despite the glass being apparently flat and smooth to the naked eye. It's not that glass is harder to polish finely than other materials, on the contrary, optical glass is formulated so it polishes very finely, but optics have to be smooth to a much higher degree than any large object.
  11. Welcome. Have lots of fun with the forum.
  12. For visual use of a Newtonian scope I prefer a dobsonian mount over an equatorial mount and so would choose the Skyliner 200p. If you do want a tripod mounted scope an f5 150p on an AZ4 mount will probably work better than a 150pl.
  13. I figured it's going to be such a largish number based on blur level of 1:1 image. 3.44" FWHM blur image should be sampled at about 2.15"/px. You could bin x2 your data to improve SNR without loss of detail. Maybe even x3 with very small loss in detail. That will improve SNR significantly and keep resolved detail about the same.
  14. Hi everyone, This is Markarian's Chain shot from my back garden over three nights in late March. Probably the deepest single image I've taken in terms of integration time...which leaves me feeling my processing is not quite doing the data justice...maybe I'll come back to it. In any case, this is an incredible part of space; looking away from our galaxy reveals countless others! The crazy number of Lum subs took a whole day for APP to chug through and so I've resolved to lower the gain from unity going forwards to get more manageable sub lengths than 15 seconds! L: 1050 (!) x 15s R: 92 x 60s G: 165 x 30s B 165 x 30s....total integration time 8.2 hours. Captured using APT, stacked in APP and processed in Pixinsight. Thanks for looking!
  15. Welcome. Have fun. Great images there!
  16. Dynamic PSF is a tool that needs a lot of hard work. After reading your post above, I think I worked out how to get the value you want (I used the PI script "FWHMEccentricity") It reports 4.41 pixels for the larger crop area in the original frame. My image scale of 0.78"/pixel therefore gives FWHM of 3.44 arcsecs. (Just out of interest, I checked a few of my other images and they come up with similar numbers)
  17. That looks like it is set up with only the 1.25" adaptor in place and so should be able to focus with an eyepiece. What happens when you point it at a star and move the focuser the entire length of travel? Do you see a doughnut of light getting smaller towards one end of focuser travel but never focusing or do you see nothing at all? If you don't see anything perhaps it is because the finder is not aligned and you are not pointing at any bright stars. Try in the daytime on the furthest terrestrial object you can see. As terrestrial objects are closer you will need the focuser position to be further out than at night but if you can get it to focus at least you can get the finder aligned before testing at night.
  18. I have seen one of these in action brilliant mounts only problem I see is if you use long fracs like me. I need a extension on my EQ5 mount to clear the tripod legs. If this could be addressed I would seriously consider getting one.
  19. Floater

    Hi

    Welcome. Have lots of fun.
  20. Hi, I'm a newbie and I've used a fair amount of hours on the web studying polar alignment now. I thought i had it after 30 minutes, but now several hours later i understand less than i did then. I have the EQ5-mount and the "new" sky-watcher polar alignment reticule, which represents a clock, but no Northern hemisphere constallations. I get the Polaris position from an app. It gives me a visual position in the clockwheel simular to the one in my polar scope. It also displays the Polaris position digitally (i.e. 01:37, which corresponds to the visual position on the clock). It gives me my local longitude (5* 15'E). Lastly it gives me the local time. From what i understand the "old" Polar reticules doesn't have the clock, but a small dot or circle on the bigger circle with constallations around it like the big dipper that you align visually with the actual big dipper, then align Polaris in the small circle? 1. The Polar alignment scope i have has a white marker line on it (Index marker ring). What do i use this for, and should it point in the 12'oclock position or do i turn on this at some time? 2. When i rotate the RA axis, the polar clock also rotate. Are the 6 o'clock position always supposed to point straight down, and 12 o'clock position always supposed to point straight up when i polar align or do i have to rotate the clock in relation to my position (longitude) or something? Like, do i have to calibrate the clockwheel orientation at any time to get accurate alignment or does always 6 point straight down like an actual clock? I dont mean calibrating to make the reticule calibrated by this, but turning around the clock reticule so that 6 o'clock is no longer in the 6 o'clock position. 3. Do i have to take in consideration that the view in the polar alignment scope is upside-down, or do i Place polaris identically like on the app? (SAM console is the app, and i downloaded it for my Sky-watcher adventurer mini). 4. The videos and articles i've read on this type of reticle also provides you a HA (Hour angle). Is the new reticle just a clock showing this HA? Or do I have to take HA in consideration in addition to aligning or is this polar clock really just showing the HA visually? 5. Some articles (this for instance: https://lonewolfonline.net/polar-alignment-equatorial-telescope-mount/ says that its important to know what date and time of the year the Polaris is at its highest altitude. Why is this important? 6. Videos and articles mentions that putting my telescope in "Home position" is important. Why is this? The polar alignment Scope is pointing the same way no matter where the telescope points. 7. As mentioned the app provides my local longitude. Is this important in the alignment process other than "Nice to know"? I welcome any answers!
  21. Been watching a science programme on BBC4 which mentioned the Challenger Shuttle accident and the cause, which turned out to be freezing cold weather affecting rubber O rings. Now I wonder if frost was the reason my ASC seals failed. Bathroom sealant is used at room temperature and not designed for large temperature range, particularly cold.
  22. And tonights winner is Sky Safari, just been trying to get a few snaps of Pallas between the clouds and SS is spot on, Stellarium way off. Dave
  23. Can't help you as I don't have one either. I was told that the Samyang with golden Ring should be avoided and the new ones with red Ring are better. The one I used was a borrowed sample of the latest version. Was ok. Fabio
  24. Anybody spot this ? bright slow and red heading east / west in area of Cassiopeia. Dave
  25. I'm so sorry for your experience but luckily the seller has been great! You probably just ran into a bad stock, which for sure speaks against Synta QC. I got my HEQ5 used and could test it before deciding to keep it, so was sure it was ok: it's belt modded now and exhibits 23arcsec Peak-peak Periodic Error and guides better than 0.6" on nights with good seeing. So you see it's hit and miss! Best of luck with your CEM25p. Fabio
  26. Hello and welcome! Given your location and viewing preferences I would definitely choose the 200p. Easy to handle and capable of fantastic views of the solar system as well as deep sky objects, you can't go wrong really.
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