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Lowest FL eyepice usable in Denk II binoviewer?

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#1 btom


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Posted 31 January 2013 - 04:58 PM

I'm getting back into astronomy after a several year forced lay-off. I decided after some trepidation to also get back into binoviewing. I used to own a Mark V but simply can't afford to go that route this time around so I'm picking up a used Denk II supersystem at a good price. This particular supersystem is a couple years old and has power settings of 1.3x, 2x, and 3x in a newtonian. The only eyepieces I've held onto after exiting the hobby were pairs of 24 pans and 12.5 HD orthos. The 12.5 Hds give roughly 130x, 200x, 300x. I'd like to use a pair of 10mm eyepieces to fill in with powers of 163x, 250x and 375x. With the Mark V I could easily use 10mm or even 7 without degrading the view. Can the same be said of 3 year old Denk IIs? And assuming 10mm FL is fine I was thinking to just order a pair of the Baader classic orthos but would like other suggestions up to $100 or so per eyepiece. Particularly those that are easy to find in used pairs. Thanks.

#2 Eddgie


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Posted 31 January 2013 - 05:16 PM

Just pick something common and buy used.

If you want new, and want to keep price under control, I can recommend the Vixen NPL Plossls. These come in 10mm.

I have a pair in 15mm and find them to be quite excellent and they only cost $30 new apiece.

The only serious issues with the 24mm Pans is that they will vignette pretty badly with the low power arm in. I found that even the 22mm Pans vignetted. 19mms worked fine.

#3 btom


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Posted 31 January 2013 - 05:58 PM

I'll try to find a good used pair before buying new. Thanks for the recommendation of the vixen plossls.

I guess the vignetting of the 24 pans makes sense since the Denk aperture is 26mm and the 24 pan field stop is 27 plus there is that long path through the prisms. This wasn't an issue with the Mark V but you get what you pay for...

Do you know the largest field stop that won't vignette in the denk II? Thanks.

#4 johnnyha


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Posted 31 January 2013 - 06:08 PM

I think the BCO 10s are a good call for binoviewing, I've been tempted myself.

#5 Eddgie


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Posted 01 February 2013 - 09:58 AM

Again, the problem is only when the low power arm is in place. For that, a 22mm to 23mm field stop is about as big as you can use without vignetting. I know a 22mm Pan vitnetted.

This was not a problem when using the system in straght through mode.

I don't know if the 24mm Pans would vignette (I think they have a 28mm field stop, but the rear port on the binoviewer is almost working as the field stop so you would not see it as vignetting, but just a slightly reduced field size).

The 22mm Pans worked great though.

So you can go with a 28mm field stop if you want, but again, since the rear aperture of the bino really becomes the field stop, there isn't much point in it.

And if you want the lowest power, you can get that with a 40mm Plossl.

I am using my 40mm and 32mm Plossls as much (or more) as my 24mm widefields. I like the brighter view. And both of these would be fine in the Denkmeiers because both have field stops very close to the end of the barrel, so once again, the rear opening of the prism housing really becomes the field stop.

#6 urassner


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Posted 01 February 2013 - 11:49 PM

I also bought a used Denk 2 about 6 months ago and have been very happy with it. I have been using D21 from Denkmeier that I bought with the Denk 2, also the 12.5 mm UO orthos. For higher magnification I have used the Pentax XF 8.5 mm and have been quite happy with them. I did not feel that the Denks could not handle the magnification. I have gotten used to the long eye relief of the Pentax and naturally of the D21. I also have 9 mm UO orthos which are quite nice, but not as comfortable due less to eye relief. The 12.5 mm orthos feel much more comfortable to me in this respect, even though the difference should not be that much.
I have not tried Baader orthos but from what I have read, they are comparable to UO orthos (at least the old ones were). Another consideration might be the TMB planetary II series, which have better eye relief than the orthos and are still on sale for $40 at astronomics.com . Have not looked through those but read many good comments. They will maybe not be quite as crisp as the orthos. The Pentax are over the price limit you mentioned ( I have seen them for $140 from Pentax through Amazon.com).

#7 Mike B

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Posted 02 February 2013 - 12:21 AM

...but you get what you pay for...

No, YOU got what YOU paid for. :lol:

If ya DON'T get what you paid for, you file charges.

Do you know the largest field stop that won't vignette in the denk II?

Don't know the measured FS value, but i've finally settled on the Vixen 22-LVWs. Probably very similar specs to the Denk 21mm EPs... they seem to work swimmingly in the Denks! All modes. No vignetting seen.

When i ran Pan-24's in the Denk, in an SCT, they vignetted noticeably in "reduction" mode. When i switched to using a Dob, the vignetting diminished greatly... tho was still there a bit.

However, the eye-relief on the Pans was pretty atrocious, and i didn't much care for their PC distortion... the Vixens stomp the Pans in pretty much every regard, especially for the Denks.

Thank heavens i did *NOT* get what i paid for... i got far more! The Vixens cost much less than the Pans, and suit my needs far better!

#8 btom


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Posted 02 February 2013 - 08:30 AM

This is very useful feedback. 22 LVWs for long FL and it appears the Denks do well down to at least 8.5mm FL. Anyway, I've backed out of the binoviewer purchase even though it was really a good deal. Decided to focus on basics first and that includes an eq platform. I'll revisit the binoviewer scene in a few months and will continue to check this forum in the meantime. Thanks all.

#9 faackanders2



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Posted 02 February 2013 - 01:18 PM

Believe the 24mm panoptics are the widest TFOV eyepieces you can get with 1.25" barrels. For wider views (with Newtonians) there are lower power switch, reducer power switch, and 45mm clear apertue 1.2x multipurpose OCS.

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