@chupathingie
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chupathingie
ParticipantYes, you are correct (I’d forgotten about the FR you have).
On a side note, UPS just dropped off my box from B&H. HFSMAN! A 405 geared head is HUGE! Much bigger than it looks in the catalog! LOL!
ParticipantThat actually tells me a lot… especially that it’s easily within range of an unmodded DSLR shooting at f5.6, since you caught this much in 4 mins at f10.
ParticipantSweet….
Amarillo, TX, United States 02/23/2012 5:51 A.M. Out For Delivery
And tomorrow night’s skies are supposed to be clear, however wind may be an issue. We’ll see, I may get lucky and be able to set up on the rim of Palo Duro Canyon Friday night and run off some frames.
Participantoooohh… I’d be interested in what the Horsehead shots look like, even if you wound up with trailing. It’s a pretty dim HA target that most astrophotogs will use a modded body or dedicated CCD to capture. Zeta Orionis can easily swamp exposures long enough to capture the emission from the area with a hi-pass filter in place. That was on my list of first-lights when I get the rest of my gear. I’m looking at framing the whole southern Orion complex hoping to get the Horsehead, Flame, M42/43 and the Running Man in one image. I’ve got the Rosette on my list as well, simply because it’s also on the list of HA’s that are normally done with CCD’s or modded DSLR’s. I’d love to find that they are within reach of unmodded gear, but I realize I may just be dreaming.
ParticipantThings I’ve discovered thus far:
The polar scope typically needs to be collimated before the first use; which basically means centering the illuminated reticle in the tube assembly so that the center crosshairs stay centered as the scope is rotated. Not a real big deal, but polar alignment will be inaccurate unless this is done properly. The scope does have adjustment set screws for this, you need a small allen key.
The reticle in the scope does not match the instruction manual. This is going to be a point of frustration for most, especially for those who have never used a polar scope before. Delta Ursa Minor (the next star up the little dipper’s handle from Polaris) is marked, as well as 51 Cephei, but are not mentioned in the manual; which shows a discontinued reticle with different marks for different stars for alignment.
The rough alignment from the polar scope is great for short focal length use, but most users’ comments indicate that a drift alignment is necessary for long exposures above 200mm. I’ve seen some impressive examples of 7 minute subs at 500mm; which is phenominal accuracy for an unguided rig (also with an APS-C sensor, so 800mm effective). I’m expecting my max FL to be at 400mm f5.6 (200mm f2.8 with a doubler) so I should be good.
hmmmm…. I’ve got an old 300D laying around that is just itching to have it’s hi-pass filter removed. That would give me an additional ~2 1/3 stops of HA sensitivity. Gonna have to see who’s published comparisons between it and other cameras modded and unmodded. Since the noise on the 300D limits the usable ISO to 800, I may actually get better results with an unmodded 5DII at 3200-6400.
ParticipantI have a DSI-II that I could fall back to if my 7D did not work.
That was my first thought with an 8″, the DSI makes for a much smaller obstruction. Part of me wishes the Hyperstar folks would offer an off-axis option. It would likely increase the image train to ~f3, but the camera could then be mounted to the side of the OTA Newtonian-fashion, eliminating the obstruction issue for all but the size of the secondary mirror.
February 22, 2012 at 5:28 pm in reply to: Acquired the first of my dad’s old Nikon lenses – for my XSi #45517ParticipantI don’t think an adapter exists that carries electricals between brands; all of the adapters I’ve ever found have been manual-only.
February 22, 2012 at 3:02 pm in reply to: Acquired the first of my dad’s old Nikon lenses – for my XSi #45515ParticipantMan, wish I coulda found a cheap adapter a few years ago when I was looking… I got raped for about $200 for one, as Novoflex was the only manufacturer I could find back then and they’re overly proud of their gear.
ParticipantBiases: This one probably isn’t useful for DSLR astrophotography-other noise sources (see above) way overpower this. Essentially, you use biases to calibrate out the base level of electron charge in each pixel. This only matters if you’re doing extreme precision or extremely low flux objects. Bias frames are taken buy keeping the lens cap on and taking photos with the minimum possible shutter speed.
Seconds on that. Althought there are many out there using CCD/peltier devices that this is still useful for.
As for darks, take 15-20 and average them. Hot pixels will stay constant, and you’ll get a very good average of the noise on the rest of the chip to subtract off of each light sub before stacking.
Lights: The more the merrier. While it is true that each additional light you take adds a smaller portion to the final image (and nudges the noise floor downward slightly), these tiny incremental changes to the S/N ratio become very significant when trying to stretch the contrast down near the noise floor to bring out faint details and wisps of nebula. For instance, in Rav‘s image made with 3 lights the noise floor is going to become apparent very quickly when the levels are stretched to bring out the fainter wisps in M42. With more subs (40+), not only will the noise floor be lower, but it will also be smoother and will show up more as a brightening of the background as opposed to hard static. At this point, simply setting the black point of the image has the effect of dumping much of that noise into the trash while letting you tease out fainter details close to the bottom of the histogram. There is always a lot more data in an image than it appears SOOC, so even the tiniest advantage you can gain in reducing the noise floor allows you to recover more of that data.
ParticipantI think I woke up Trish…and started a coughing fit… damn that’s funny! 😆
ParticipantHow about the barrel rolls the hummingbird does when the bee comes around? This is a farking awesome video, thanks!
I caught that on the first pass. That’s the definition of agility, right there. Watch the stability of that bird’s head while the body spins and the wings compensate. Amazing.
ParticipantI’m not gonna mess with my sig… it works, dunno why, and I ain’t gonna break it!
Participantohshit…don’t get me going… a parsec is likely the most obtuse measurement ever conceived… it’s practically arcane, but roughly equal to about 3 1/4 light years. The nearest star to Sol is about 1 1/4 parsec. I’ll leave it up to y’all to gather scale on that. Do a wiki to get the definition, it’s an odd standard for measurement, but a standard it is nonetheless.
ParticipantDamn! that was purty. I especially like the bats eating the cactus nectar. One was carrying a baby bat!
Yeah, I agree… and I had to go back to catch the “baby on board” shot… I blew right by it the first time around!
Participantgotta add: the core is not overblown…the Trapezium isn’t lost in the brighter parts of the nebula.
Red is emission, hydrogen gas excited by the ultraviolet from “nearby” stars; blue/grey is reflection, gas and dust illuminated by, or obscuring light from, the stars in the area. Very nice, it’s easy to see the 3d nature of M42 in this image…
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