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Hasselblad posted:Yup. Once I learned you could set it at the 12 o'clock position via a small level on the counterweight bar, and then on the dovetail it worked out. At least trial-run-wise as the setup still has not been outside yet. Trying to determine the illuminated cross hair eyepiece I am going to get. The ones with better illuminator pieces tend to have single cross hairs, while I really like the idea of the double cross hair for alignment on a star. All of the ones on amazon look like they have poo poo manufactured lights. The cheap Astromania one on Amazon has the double cross hair. The optics probably aren't great, but all it's for is putting a star between some cross hairs. My mount has star alignment and a polar align mode, so I've had good results (>60s unguided photos) just eyeballing Polaris and then running the polar alignment program once or twice with a reticle. It's physically difficult get the alignment just right by turning the screws, especially the altitude knobs, so I'm not sure I could do any better with drift alignment or a camera. It's fiddly enough that I don't think the single cross hair would really matter.
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Apr 3, 2019 05:13
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Golden-i posted:I went with the Celestron Advanced VX mount that shipped with their 8" reflector scope and one or two eyepieces, which is in the ~$1250 range, I think. I got a very similar setup except with the 6" telescope option for $820 on sale, and I like it pretty well. Tracking isn't perfect but I've gotten some pretty good photos. One thing to keep in mind is that the mounts all have published weight limits. This is the weight for your equipment, not including the counter-weights, but it does include the telescope and any cameras and other gear. The Celestron AVX (and similar mounts in its weight class like the Orion Sirius) is rated for about 15 kg of gear, but various online sources suggest sticking to about half the weight rating for photography. The 6" telescope version is about 5 kg, while the 8" version is about 10 kg, which was the main reason I went with the smaller model. People often end up adding a second smaller telescope for guiding (I adapted one out of a $10 telephoto lens I found at a camera store) so the weight can add up. If I was doing this again from scratch, I'd probably get a mount by itself and buy a GSO telescope like this since it looks much better made than the Celestron version.   
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Jul 25, 2019 21:28
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Dick Trauma posted:This might sound like a strange question but when you are setting up these photos what do you actually see? There's a lot of light pollution where I live, so looking through an eyepiece these sights are at best a fuzzy blur. Still amazing, though. When taking photos, I need to carefully balance the scope with the camera on it so there usually aren't any eyepieces involved. I took those photos with a DSLR, and with the ISO cranked up all the way with live view, I can see a fuzzy blur, but of possibly dimmer objects than I can make out visually. More recently I've just used plate solving to point the telescope, so the first shot is a decently long exposure. Here's a single frame from the Whirlpool Galaxy shot above, as the camera saw it. It's about a 30 second exposure (I think), with a UFO. You can see the galaxy if you squint:  After stacking together about an hour's worth of these photos, Siril produced this image:  Then finally, I set the black point and played with the histogram etc. and cropped to produce:
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Jul 26, 2019 00:43
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Luneshot posted:However, for astrophotography refractors have better contrast for a given aperture, and no diffraction spikes. Personally I like the diffraction spikes, but your preferences may vary. Contrast for a given aperture always seems like a weird metric to me, since for the same price you're comparing a small refractor to an enormous reflector. A low-end 80 mm APO refractor costs in the same range as a big 250 mm newtonian. If you go up to the fancy 130 mm imaging refractors, it's $3,000-$6,000, vs. maybe $100-200 for a similar size reflector. Or for $3,000 a... uh... 250 mm truss Ritchey-Chretien astrograph. Obviously this is dumb since you need a $10,000 mount for a telescope that big, but the point is you're never comparing two things with the same aperture. You can take good pictures with a newtonian, it's just very fiddly compared to a refractor. You need to get the collimation just right especially with a coma corrector, there are back focus issues, balancing issues, etc. I grew up with a newt on an equatorial mount so none of this stuff really bothers me, but I can see the appeal of only getting mad at your tracking mount instead of your mount and your optics at the same time.
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Jul 26, 2019 21:35
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Golden-i posted:I've got a question about PPEC if anyone can help me out - I'm trying to understand the fundamentals of it before I try applying it. My understanding is that the mount needs to be parked between uses for the PPEC/PEC curve to continue to apply. Does that mean that if you move the mount with the clutches engaged between uses, you'll need to re-do your PPEC/PEC recording? Maybe someone who knows more has a more definitive answer, but my understanding is that PEC is just to compensate for mechanical variation in your particular stepper motor and worm. Since the motor has an encoder in it, as long as it's permanently meshed to the worm it shouldn't matter what you do with the clutch, just if you take the mount apart or replace the motor etc. At least on my mount the clutch just disengages the worm from the actual rotating head so it can spin freely. The mount still knows where the motor is on the worm, it just doesn't know how that relates to where the telescope is pointing. Unless you have a super high end mount with absolute encoders, anyway.
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Jul 27, 2019 08:43
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Golden-i posted:Though the coma corrector seems like the best choice at the moment, it's cheaper than a new scope that won't have these issues and I'm still not sure what I want in my next scope. I remember finding a review at one point comparing different coma correctors, and the conclusion somewhat surprisingly was that the cheap GSO one worked better than the Baader for half the price. Myself, I designed my own coma corrector based on a random forum post using a program that only works in French (thanks Google Translate!) out of $20 lenses, but haven't gotten it and the telescope quite collimated right yet. 
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Aug 7, 2019 04:34
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Rolabi Wizenard posted:You're going to put a long (long) tube on an equatorial mount for AP purposes? That mount will have to be a $1500 EQ-6 class or better, and the tube will have to be sturdy to prevent flexure. They spec a PVC pipe. Also notice that the test photos were of the moon, by far the easiest thing to image in the sky. You don't need a $1,500 mount to image the moon, because it's so bright you can use 1 millisecond exposures. Any old mount including a cheap camera tripod will work if you just need a 1 ms exposure time.
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Aug 15, 2019 07:49
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Hasselblad posted:Some of us just like the ability to walk outside and stargaze without human-caused clutter. This is literally an affront to anyone looking up at night. As I walk outside in my Bortle 9 light polluted skies half an hour after sunset, the blazing sky glow is so bright that I can easily read even in full darkness. As I have been my entire life, I am confident I can see without a flashlight, safe from any danger. I look up, and quickly spot Rigel, Betelgeuse, Sirius, and can just barely make out Orion's belt. These are the only stars I've ever seen in the Spring sky, even with a new moon. To the west, Venus shines far brighter than any of them, a glaring pinpoint almost painful to look at. Looking back to the few stars I can see, suddenly a brief twinkle catches my eye. A satellite, glinting briefly in the setting sun before it goes dark in Earth's shadow. Those bastards, those repugnant fools, utterly ruining the night sky that is my birthright! I raise my fist and scream incoherently at the affront. A moment later, one of the six airplanes visible above the horizon goes overhead and the roar of its engines distracts me. I simmer down, and enjoy the blinking colored lights, so calming and soothing. Then I set up my camera and take some photographs of M31, easily filtering out any airplanes or satellites by clicking one button for sigma clipping and using the defaults.   Even with hours of exposure time, the result still looks like rear end due to sky glow but hey what can you do. (Note: Actually I live in Bortle 8 skies and can see literally dozens of stars!)
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Apr 15, 2020 00:06
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colonel tom posted:Hello thread. Is there any reason a mirrorless camera wouldn't be suitable for hooking up to a telescope? A mirrorless should be fine and work about the same as a DSLR. Just like a DSLR you'll need the proper t-ring which should cost about $10, and some adapter bits. A mirrorless will require less back focus than a DSLR due to not having the mirror, which is good and easier to mount since some telescopes are limited. Also like a DSLR, look into how you'll control it, either through a remote clicker for simple stuff, or with a computer and USB. There are probably people using whatever camera you're considering with a telescope already, so you can search around to see if they had issues. At high magnification like you typically get with a telescope, you usually need an expensive robotic EQ mount, possibly with active computer guiding, not just a star tracker. You can get some really fun images of the moon or maybe planets without the expensive kit though.
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Mar 28, 2021 19:58
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Salt Fish posted:Tell me a bit more about mounts. I feel like a full goto is cheating, but are you saying that a motorized mount with good alignment would only give you a few minutes of exposure without streaking? A nice goto EQ mount (or maybe an alt-az with a wedge) is usually considered the minimum to do long exposures. By long exposures I really mean 1 second or more, though it depends on the focal length. With a 50 mm lens, you can get by with a star tracker, but with a heavy 600-1800 mm telescope it can be hard to avoid streaks even with a fancy mount (and you may need active guiding). You don't technically need the whole goto function to do photography -- you really just need good mechanical construction and a steady RA motor -- but any mount like that also has a goto handset these days. Theoretically it's possible to modify a manual EQ mount but that would be pretty advanced stuff for most people and still expensive. Historically back in the film days people even did hand-guiding by looking through a second telescope but that's... impressive. It's possible to use a goto alt-az mount as well, but you'll get field rotation on long exposures and the low end ones aren't really meant for photography. In addition to having a decent mount, you need a spot on polar alignment to do even 30 second exposures. People who are somewhat serious about this generally drive the mount and the camera(s) using a laptop (a raspberry pi can work too) and use software assistance to get the polar alignment right, plate solving to make sure their target is lined up properly, and a second camera to do autoguiding. Goto mount software (or just drift alignment) can help you get a good alignment though, and I was certainly able to get some nice photos with just the telescope, mount, and a DSLR without all the fancy stuff. The minimum mount that'll work with a small to medium size telescope is something like a Celestron AVX or various other options from Orion, iOptron etc. around $800, though some people swear you need to pay $1500-2000. There's practically no upper limit, you can spend as much as a car on imported Italian telescope mounts for your optically perfect telescope hand made by master opticians if you want. These mounts are also pretty heavy (even relatively portable ones like iOptron makes) and take a while to polar align correctly, so it can be a real chore to set them up. E: typo Tyrgle fucked around with this message at 20:22 on Mar 29, 2021 |
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Mar 29, 2021 07:09
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