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About Lokifish

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    Central Eastern U.S. under SQM 16.4 skies
  1. Afocal DSO shots, with a cellphone on an alt/az. I can hear the screams of "you can't do that" from here.
  2. If you want to test your lens; Print the targets Place them on a flat surface at least 25ft per 500mm EFL away (the further the better) Space them so the fit edge to edge in the camera frame (Bob's article shows examples) Make sure everything is aligned (the closer the camera is to being perfectly face on, the more accurate the results) Make sure you are in focus and take some shots From here you can figure the resolution as follows; Divide image pixel width by the 100mm line's width in pixels in the image Multiply the above result by the sensor width in mm Multiply the the above result by the lowest resolved group If possible, confirm the lowest resolved group by using an eyepiece on the lens The result is the lp/mm. If using the updated chart from the second post, find the lowest visible contrast for the same resolved group. This gives the single shot lp/mm and contrast for your lens. Share your results, and the image if possible. I'll periodically update the list and have the entries link back to the appropriate posts. When I get the chance I'll do a "baseline" using a common telescope, or two, and add it to the list. This should help folks get a better feel for what to expect when using a mirror lens. Thanks and clear skies
  3. I've added a pinpoint positive and negative chart (example below). It adds a contrast resolution chart in 10% steps and is far less forgiving than a bar chart.
  4. Questions like "600mm Mirror Lens for Astro?" pop up from time to time and feedback is often no more than "I like lens X". To help folks narrow things down I've put the Modern Photography mirror lens tests into a sortable list. While somewhat out of date, it covers the bulk of older lenses one would find on the internet. What's missing is most LZOS Rubinars, Opteka/off brand 800, 900 and 500/6.3 lenses, and some more obscure lenses like the Contax/Yashica 1000/10. While not the exact same chart, Bob Atkin's lens testing guide can be used for those wanting to submit their own tests for inclusion into the list. I have created a resolution/contrast variation test target which includes 100/80/60/40/20 percent contrast targets and cleaner lpm targets down to group 9. This should give reasonably accurate lpm results but contrast will be a more general 20% grouping. I may update the chart later with a finer contrast scale and inverted values. I will also add that this is where tiny pixels shine if doing photographic tests. A prime example is while testing alterations to my Sigma Ultratel (late model) 500/8. It took using a 1.12um sensor to even come close to visual tests with a 10mm Plossl without a lot of stacking and editing in post.
  5. Celestron LCM mounts are an often overlooked resource for shorter focal length AP. Not much bigger than a tracker, costs next to nothing, has tracking and goto. With a load capacity of around 5lbs, an MTO 500/8 is probably about the heaviest/longest lens one should put on it.
  6. The SLT has N/S EQ modes like the rest of the Nexstar+ series. So it's just a matter of putting it into EQ mode and doing goto alignment. By default, it's tracking is pretty bad so even a webcam guider w/ 40mm FL lens makes a significant difference.
  7. Thanks. I purchased the H-C for $20 (the fungus and finger prints on every optical surface came free) as a project. It's original purpose was to make a cheap table top telescope for my 4yo. The AP I did with it was more to prove a point. Heck, I didn't even shoot flats or darks for that image and lost a lot of data to compensate. Shooting under SQM 16.4 skies didn't help matters. But as a response to the often read "thousands of dollars", it performed well. Here's the wedge. It's definitely DIY and pretty basic. Heck, even the guider is a modded webcam hot glued to an old CCTV lens I had laying round. I think as a last hurrah I may do a proper imaging session and use the results as a lid insert in the carry case I plan to make for my daughter's telescope.
  8. Well seeing you can't post wedge mounted fork images in the no-EQ thread, I'll leave this here. The only reason I did it was I was repeatedly told that long exposure AP can't be done on anything short of an EQ-5. This is first light for a wooden wedge carrying an SLT Alt/Az. So yeah, orders of magnitude lower on the pecking order than even an EQ-3. This was also done with no polar scope, finder, index marks, or drift alignment. 220s single exposure @ 400ISO (NEX-3) 62mm f/8 Houghton-Cass (AKA 2nd generation Sigma Ultratel 500/8) The Sigma has some pretty bad astigmatism in it's original configuration, so those weird shaped stars are more the lens than anything else.
  9. So the same mod one would make to an older Celestron controller (solder leads to direction button contacts, terminate leads at an RJ11 port, cut space for RJ11 socket in controller)? If so, that's great. It also makes me wonder where all the "you need an Arduino or relays" stuff came from that I found when researching this.
  10. Can an LX5 (with the XL quartz drive) can be modded to accept ST4 guiding. Not talking programing an Arduino or making my own PCB with relays. Just the basic ST4 port mod like you can on older Celestrons. I am looking to upgrade my current rig and (despite what many may think) a fork that can be guided and yield 300s exposures is the perfect tool for the job for me. I'm not posting this out of the blue either. I've dug through forums, internet archived sites and forums, and info on Meades in general is fairly lacking. The best I've found is can/can't arguments but nothing concrete. Hopefully somebody here knows the answer.
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