Posts Made By: Mike Neus

Steve, the telescope you describe would be a Meade 628. I have a manual for it and the mount somewhere, email me [email protected] if you want a copy. Trust me though, you aren't missing anything! This mount was common to the 625 (6" f/5) through the DS-10 and IMO is superior to the Star Finder equivalent. It's probably not worth much due in part to age and the dob revolution.

Being tired of smashing my eye against the eyepiece for high power views, I am seeking a pair of eyepieces primarilly for planetary observing. One eyepiece of about 4mm and a second of about 7mm. I desire reasonable, but not necessarilly long, eye relief (>10mm desireable, as low as 7 would be OK). Budget is lets say <$150 per eypeice, but more is possible if I'm convinced it get's me somewhere. They will be used on an 8" f/6 newt with mighty darned fine optics (if I say so myself).

Options I've found:
1) Vixen Lanthanum 4 and 7mm
2) A pair of longer focal length Ortho's or Plossls w/a high quality 2-3x barlow or power mate (any particular combinations here that work particularly well?)
3) Takahashi LE 7.5 + televue or ultima 2x barlow
4) Siebert Standard 7 and 3.9

Any ideas on which is best from a contrast and detail resolving standpoint? Any other options I'm missing? Thanks.

Question on 500mm-ish telephoto lenses for piggy back astrophotography. Has anyone tried a 500mm f/8 telephoto lens for astrophotography such as this one?

http://www.adorama.com/catalog.tpl?op=details&sid=10425104512240097&sku=SY5008PU

This same lens appears to be available under 3-4 brands for about the same price and can be had either in mirror format or the more conventional "all lens" format. Is there reason to believe one design would be superior to the other?

How about this one? The main attraction of this is the faster f/ratio, but it costs a bit more.

http://www.adorama.com/catalog.tpl?op=details&sid=10425104512240097&sku=PRO500

Are any of these viable or am I better off with something like a Synta 120 short tube OTA (600mm, f/5) for about $300? I understand that probably none of these will be perfect particularly near the edges. Perfection I seek not, but will they produce reasonably good results? Thanks.

I posted this in the astrophoto section but haven't got an answer, hence my query here. Has any one used this item (or it's Orion / Celestron twins) for piggyback astrophotography? Is it any good? Thanks.

http://www.adorama.com/catalog.tpl?op=details&sid=10425104512240097&sku=PRO500

Anyone notice Celestrons new line of eyepieces? Reads an awful lot like the Orion Epic line but these claim to be corrected for scopes up to f/4 and the focal lengths are different. Anyone know what these are? Seems like a bargain if they're as good as claimed.

Fernando, TREAD CAREFULLY. When selecting eyepieces it is very important to consider not only magnification, but true field of view as well. A higher power eyepiece with the same true field of view as a lower one will **usually** be perferable. You will see just as much sky but with more magnificaiton, translating to more detail and contrast.

Remember:

Mag = FL(telescope) / FL(eyepiece)
TFOV = AFOV / Mag

With this in mind, you should revamp your eyepiece collection. Replace your 40mm with either the 30 or 32mm plossl you mention. The 40mm has no significant advantage in a 1.25" eyepiece. The field of view is restricted by the barrel to an AFOV of 40-45 degrees. A 30 or 32mm will have the full 50 AFOV resulting in a similar true field of view as the 40mm. Since a 30 or 32mm eyepiece is close (magnification wise) to your 25mm and with a barlow comes close to your 17mm, you have also obsoleted two other eyepieces. You might consider replacing these with a single 22mm-ish eyepiece to fill the gap, giving 30, 22, 15 (30 w/Barlow), 11 (22 w/Barlow), and 6mm which is a pretty decent selection.

If you mix wide fields into the fold, be careful about mixing them with your plossls. You could easilly make several of them obsolete. For example, the 21mm Siebert you mentioned and a whole host of other wide field low power eyepieces will very probably provide as wide a true field of view as the 40 (or 30)mm and wider true field of view than the 25mm. There is then little advantage to keeping those eyepieces. Likewise, the 10mm Siebert might trump the 17mm Plossl. You'll just have to run the numbers and see.

The Siebert standards are generally speaking very good performers. I have his 15, 12.5, 10, and 7mm and have no problems recommending them. The only distortion visable in any of them is right near the field stop where some astigmatism is present. I have heard mixed opinions on his 21mm. All I can suggest is to try them. Siebert has a 30 day return policy that I did use once with no problems what-so-ever.

Thanks for all the inputs. At the moment I think I'm leaning towards the Nagler Zoom. Breaks the budget a bit, but it sounds like it's worth it. Mike is right, the reviews say this is a killer planetary eyepiece.

Anyone have experience with the Vixen Lanthanums or the Siebert 3.9 (I know how the 7 does, I have it). That's about the only input I'm lacking.

Thanks again!

Here is a picture of Saturn I took with my Meade 826, an 8" f/6 newt circa 1985.

http://www.siebertoptics.com/SiebertOptics-astrophotos.html

Hey all, me again. Well it seems after checking the news groups the 500mm mirror lenses are generally considered pure rubish, but the pure lens design is said to be quite good and used they are a song. My only regret is the longish photographic speed (f/8).

Before I leap into this I just want to ask if any one has the Pro-Optic Maksutov mirror lens. I gather that it was also sold under the Orion and Celestron brands as a spotting scope and the mirror is columinatable (is that even a word??). It's much faster at f/5.6. I'm concerned it may have the same faults as the cheap Vivitar/Pheonix/Quantaray etc mirror lens (i.e. poor optics, given the price point). Can anyone confirm or deny? Thanks.

Don, I asked a similar quesiton in the eyepiece group not to long ago. I received a number of votes for the Tak LE line and the Nagler 3-6 zoom. A cheaper option if you already have a good 16mm-ish eyepiece (Ortho, Ultima) is a high quality 2x barlow which is what I decided I would try before sinking more $$$ into more expensive eyepieces.

Celestron Ultima=Orion Shorty Plus are reputed to be excellent barlows for about $70. Antares 2x is said to be the same barlow less the grip ring for about $55 (I'm still trying to figure out why used Antares show up here for more than the new price). Televue 2x can be had used in the same price range.