Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.


  • Content Count

  • Joined

  • Last visited

Community Reputation

89 Excellent

About laowhoo

  • Rank
    Star Forming

Profile Information

  • Interests
    36mm Baader Hyperion; 31mm Baader Hyperion; 24mm ES 68; 18mm Baader Classic Orthoscopic; 11mm Nagler T6; 8.8mm ES 82; 4.7mm ES 82; Siebert 1.5x Barlow; 12.5" f/6 binoscope, Terry Ostahowski primaries/secondaries; IStar star diagonals; Orion Ultrablock, SkyGlow, 13% moon filters // Pentax PCF 12x50 and 20x60
  • Location
    NJ, USA
  1. LOL. Can you be more specific? Well, I did manage to find this thus far Doesn't sound very well endorsed as an astro app. But I'll read this http://www.baader-planetarium.de/news/mirror-Prism-Dielectric-Diagonal-Comparison_2014-03-06_v2.pdf Cheers
  2. What people say is predicated upon both computational optics (Sacek) and experience (Seronik), hence my inclusion of both. But I'm perfectly willing to run the experiment myself, and even to self-delude (I do it all the time), regardless of neither knowing how nor why my experience may or may not comport with what's been established otherwise, or when it's doing or not doing such. But thanks? And guess I'll just fire off an email about the prism/frac, so thanks again? Any reason why one frac or another will or will not benefit thereby? Or maybe when? Is it a doublet vs. triplet thing? Most helpful (see your avatar).
  3. Ugh. Stopping down bigger apertures for atmospheric turbulence? Well, I'm gonna have a deeper look...again...never mind that Gary Seronik and Vladimir Sacek say otherwise http://www.telescope-optics.net/seeing_and_aperture.htm#MTF But my question is about the prism diagonal. We're getting our first frac and will have to look into this. Thanks
  4. That's what I was thinking. Can't imagine having a Mak and not looking at the moon, at very least.
  5. Yay. Was thinking there was something wrong with my eyes, what with all these uber-wide, uber-priced super-duper wide fields. Not slamming those, but if we can save half by simply looking through the EP so much the better. BillP very favorably reviewed the Morpheus and thought we were gonna have to swap out. https://www.cloudynights.com/articles/cat/user-reviews/the-baader-planetarium-morpheus-r3003 and having just received his will be doing a follow-up review of these. Following to see how you like them.
  6. Mels graphic calculator (his whole site) was down earlier but is up again. Try this http://www.bbastrodesigns.com/diagonal.htm I plugged your numbers in for a 63mm 2dary, 9 inches from it to focal plane of an EP w/ 36mm field stop, and your illumination numbers are better than ours (should be for our added light path--we barely squeaked in). Even if you're 10" from the 2dary your numbers are great. No way you should go bigger. (Hyperion 36mm 72 FS is listed as 32mm.)
  7. Sorry. TLDR answer is no, the opposite is true. The greater CO will degrade precious contrast on DSOs, and your illumination field maxima would only apply to low power wide field EP field stops. Best compromise would be a middle choice size of 20-25% for all things including collimation, and full offset will help for illuminating your big EPs. I use LocTite 2-sided tape--the 110 pound variety. Used it originally (lesser strength) and just remounted mine (5 years on). It sticks better with time as I could barely get it off. Also provides the spacing you need, but we're not clamping, just adhering to lightweight stalk. Which 2dary did you get? We're 12.5" and were encouraged to stick to 1.25" focuser w/ 2.14" 2dary (smallest), but we easily balked at both and are still only at 23% obstruction with 2.6". Used Mel Bartels calculator with the Stellafane raytrace for 36mm72 EP and get excellent 75% illumination, even after going through a star diagonal. Re: real world use/handling, we don't often get to use our largest EPs so our 75% illuminated field shrinks in practice, and we're a more forgiving f/6 for collimation. Besides Bartels and Lockwood we also consulted Royce http://www.rfroyce.com/diagsize.htm Here's the tape https://www.amazon.com/dp/B003U2B5EA/ref=asc_df_B003U2B5EA5364191/?tag=hyprod-20&creative=394997&creativeASIN=B003U2B5EA&linkCode=df0&hvadid=198062181806&hvpos=1o1&hvnetw=g&hvrand=4297119983086375083&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9003932&hvtargid=pla-391176935453 Re: your Q about faint extended objects (DSOs) there's this http://www.telescope-optics.net/telescope_central_obstruction.htm In brief, you could go 30% CO w/ perfect optics and still retain a Strehl equivalent of (only) .80 wh/ is why most people try to stay around 20-25% (except for planetary). There are averages at play (esp'ly seeing) that will make real world vary from these formulations, but we wanna be ready for those great nights and dark skies, and w/ 12" you've got a DSO hunter so I think I'd err on the smaller side if possible and learn to love collimating. Moreover, your illuminated field will be smaller than you think b/c you won't be asking this using your lowest/widest EP, etc. You wanna be able to use your 4.7mm on a planetary nebula on a good night. Decide whether you want convenience and want to fully illuminate (100% and 75%) your big EPs, or whether you wanna maximize for high power on faint fuzzies. Jetstream went the next size up (as we did) and was still only 22%, so if you have 3 sizes to choose from, no way I'd go biggest. I'd be middling, and a good compromise for f/5. And as he also said, go full (classical) offset to get all or most of the illuminated field for your big EPs. Cheers
  8. We ordered the ES 40mm 68 last night, for the new frac arriving soon, and even tho we're already using the Hyperion 36mm 72. Just didn't feel right leaving that last little FOV on the table, or not letting the frac shine to its full potential. We're already using the ES 24mm 68 on the Dob and b/c it edged out the Panoptic in one review/shootout. Expecting great things.
  9. Congrats Tareq. Use these free programs for now http://stellarium.org/ https://www.ap-i.net/skychart/en/start or this for your Mac or android https://skysafariastronomy.com/
  10. Mad dogs and Englishmen. I built a sled for the scope Catman, not a house. Now you've put me in mind of a small gauge train that the kids ride--straight out to the center of our backyard. Do you suppose the house will sell for more, or for less, having had an eccentric old man in it (meaning me)? My wife's very understanding, and I better keep it that way. But I admit to already having seen your build, after which I tested those waters with her, and her smile said it all.
  11. Probably my favorite online calculator http://www.stargazing.net/naa/scopemath.htm gives you lotsa good things, including theoretical limiting magnitude for stellar objects, brightness factor for extended objects, theoretical resolving power of seconds of arc, and more (theoretical size of moon features, etc.). Just plug in your aperture, focal ratio and EP.
  12. Excellent link. And another (page you might have seen floating around, borrowed from Suiter's Star Testing) re: primary aberrations
  13. LOL We just did the same. Why? I have NO idea. Probably too much time at this site. But I can't wait (5 days) to see the difference. Pretty much deep sky so maybe I felt the tug to spend time closer to home? Better for road trips, too, and my wife and I can view simultaneously. Honestly, tho, spend enough time in this and I can see why so many have so much. Now all we need is a Mak.
  14. At f/5 (correct?) I think I remember your primary axis error tolerance (PAE) to be about .85mm or thereabouts. It's charted somewhere on the net, but you can be nearly a mm off axis w/o any notice of image degradation/contrast loss. I don't remember now whether primary aberrations also follow/show up (coma, TDE, etc). Nils is the boss (RIP), and Don Pensack and Vic Menard also rule for collimation. Another must http://www.telescope-optics.net/ And for fun, check out Suiter's Star Testing for a classic breakdown of collimation errors and understanding. Google PAE for your focal ratio. edit: Here's the chart https://www.catseyecollimation.com/Newtonian Axial Tolerances.pdf and f/5 has an error tolerance of .63mm Cheers
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.