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Denk with DSO's

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#1 REC

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Posted 28 September 2013 - 08:34 AM

Well after doing some whining about BV and the Denk2 Super System and Reading tons of comments here, it was time to just go do some observing. We had a very clear night last night ans the seeing was good too. I recently just bought a second Meade 20mm SWA to pair up. Otherwise I have been using a pair of 26mm SP for DSO's and they are ok, but wanted the more imersive view from a 68* EP. So after I took the shrouds off the EP's I was able to fit the bridge of my nose in them, plus 25% lighter.

So first I checked out some clusters in Sagittarius, not bad at all through the native straight through mode and also with the reducer arm in. The EP's seemed to be pretty sharp to the edge...as far as a Newt can be (coma) and pretty good contrast.

Next I left the reducer arm in and just did some cruising up in the Cygnus area straight overhead....stars, stars and more stars. I can see that this is going to be fun with some DSO's in the wider aperture from the 10" Dob than the narrow FOV through my 8" SCT and perhaps brighter even though I have to use a 2x OCS in it. Sure would be nice to use it without, but I don't want to mess with the scope and moving mirrors ect.

Ok, 11pm now and Cassiopeia was high enough over the horizon to escape some of the light dome LP I have in the east. (Sure be nice if we had a black-out one night...LOL)

So, after searching back and forth the sky I was able to find the Double Star cluster. I had the reducer arm in and was just able to fit both parts of it. Nice black sky background and my eyes where peeled to the EP! Then I tried it straight through and could only fit one cluster at a time in it. I can't wait until next month when it's higher in the sky not so late in the night.

So yeah, the Denk2 in the reducer mode is something to behold for the brighter DSO's in this scope. Tonight I'm going to try the 26mm SP's in them and also a mixed pair of 32mm on the cluster and see how it does. Also will track down a few of the brighter Globs and see ow they fare in them.

All and all, a very enjoyable evening :)

Clear Skies to all!

Bob

#2 Eddgie

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Posted 28 September 2013 - 09:53 AM

I can see that this is going to be fun with some DSO's in the wider aperture from the 10" Dob than the narrow FOV through my 8" SCT and



Yes, this was one of the reasons I went to the 12" dob from the C14. Wider fields of view.

That was not the main reason, but it was a heavy factor.

I think even with OCS, an f/5 or so dob is the best possible Binoviewer platform.

Enjoy.

#3 REC

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Posted 29 September 2013 - 09:32 AM

So last night my neighbor was having a party on his patio and had some lights on (normally off)so I was limited to the NE sky that was still pretty dark. I had recently paired up my Meade 20mm SWA ep's and decided that the view with these was better than the 26mm SP pair I had been using for DSO's.

So with the low power arm in, I was content on cruising the Cygnus to Cassiopia area. Very nice tight stars against the black velvet sky. Finally settled on the Double Star cluster. I had been looking at it earlier with just my 28mm EP and noticed that both clusters were not very sharp at the edge. I figured that is was just the coma due to a 10" Dob standard performance and I'll to check the collimation of it the next time I go out. BUT, with the 20's in the BV I was pleased to see that both clusters where sharp!

Now with both clusters just fitting in the BV, the view was just stunning...the best I have ever had I believe. I'll have to compare it with my 8" SCT with a wide angle EP again. I then just viewed it with the arm out and straight through, but then I could only fit one of the clusters in the FOV...back to the reducer arm. liked that better.

Tonight I'm going after some of the brighter clusters, nebula's and Globs!

Bob

#4 mark8888

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Posted 30 September 2013 - 07:37 AM

Tonight I'm going after some of the brighter clusters, nebula's and Globs!


Better to go after the Globs, than the Globs going after you! :grin:


Sorry couldnt resist. Great report. I also love binoviewing the double cluster, it's always amazing.

#5 REC

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Posted 30 September 2013 - 10:27 AM

Mark, what are you BV with?

#6 ur7x

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Posted 14 October 2013 - 09:25 AM

I'm new into this whole Bino viewer thing. But I can add that a pair of simple 28mm eyepieces and a nice Denk Bino on my 9.25 has opened things up considerably for me.

First off the simple comfort of looking with both eyes can't be underestimated. Next the ease of visual resolution you get with two eyes is also huge, our brain simply resolves images better this way, why fight it?

I bought these primarily for planetary and lunar viewing... After experiencing a Bino View on a old friends setup earlier this summer. This morning, on a bit of a lark I decided to see what M42 might look like with both eyes... in a word... STUNNING... and this with next to zero night vision. In very bright predawn in VERY city light polluted skys.

Then over to Jupiter... Wow... simply WOW. As others have posted on other threads with a simple 2" diagonal and 28mm eyepieces I get larger magnification with the Bino setup then I would with a single 25mm 2" eyepiece in the same diagonal. I could calculate the actual number based on the added focal length of the Denk setup I would guess that simply straight through the Denk is about 1.5X-1.6X more powerful.

I'm sure that on some scopes these work better than others, but in spite of that, would recommend a Bino system on ANY scope that you can reach focus.

They are simply amazing on my SCT!

#7 Eddgie

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Posted 14 October 2013 - 09:37 AM

I have become convinced that using binoviewers makes far more difference in the ability to do good planetary observing than what eyepeice you use.

I did not always feel this way. The first time I used binoviewers, I thought I was able to see the same detail as with mono and in fact, perhaps a bit more in mono.


In retrospect, the equipment was not the best and the configuration was contributing to some performace issues with the scope.

Now that I have ironed all fo that out, I am convinced that for planats, binoviewers make a far larger difference than what eyepiece you use in monovision.

And the more I did deep sky with binoviewers, the more I came to desire using them.

I don't miss my Nagler's either. I find that even a 68 degree apparent field when binoviewing seems more than enough. You can more easily take in the entire field and it just seems so natural that I simply haven't felt the urge to use Naglers.

As for wide true fields, I am now using my 12" at a 2550mm focal length (1.7 GPC) and this sounds bad, but the full moon fits easily, and of the 2000 or so targets that will be decent targets under my own sky conditions, I would estimate that 1900 of those will more than easliy fit into the field of the 12" even with a 1.7x GPC.

And they all look great!

Enjoy!

#8 Sarkikos

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Posted 17 October 2013 - 07:19 AM

I think even with OCS, an f/5 or so dob is the best possible Binoviewer platform.


That is my conclusion, too. Nevertheless, the general concensus seems to be that Cats are best for binoviewing, then refractors, and lastly Dobs. Some observers even appear surprised that I only binoview my Dobs, not my Cats or refractors. :shrug:

My best scope for binoviewing is my 10" f/4.8 Dob.

Mike

#9 Eddgie

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Posted 17 October 2013 - 08:16 AM

Unless you can reach focus without a GPC, using them in a refractor seems like such a waste to me.

For me, the only place were refractors are truely superrior is in their ability to present wide, coma free, well illuminated fields of view.

In my 6" APO, I get an amazing 2 degree true field than not only fits the Double Cluster in, but frames it with a huge field if faint outlying stars. And stars everywhere are tiny pinpoints of light. You just can't get that view with binoviewrs sadly. Oh but if you could...

And as for the SCT, the field of my 8" EdgeHD with binoviewers is only a tiny bit larger than the field of my 12" dob.

Because the BVs force the EdgeHD 8" to work at a focal lenght of about 2275mm, when I use the same 24mm eyepeices in each scope, the power is 106x in the 12" and about 94x in the Edge HD, and that is even with the 1.7x in the Newt.

And when you compare exit pupils, well it is simply no contest. At 106x, the Newt is a decent 2.88mm in the Newt, and only 2.1mm in the 8" (and this is indeed calculating in the fact that I am only working at 200mm of apeture in the EdgeHD, which is the best I can get witout an OCS).

And if I go to the 35mm Ultima in the BVs, I get an even bigger true field, and 73x with a very big 4.17mm exit pupil, vs the 65x and 3,1mm exit pupil in the 8".

And mananyone using binoviewers with some kind of reducer in their scopes (Glee, low power arm, 6.3 or whatever) are using scopes with less than full apetuer, turning their scopes into instruments with between an ince and and inch and a half less apeture, while the Newts always work at full apeture.

All scopes have thier limits, but using a 1.7x GPC on an f/49 dob turns it into an f/8.3 instrument. Using it on a C8 turns it into an f/11.5 scope, and using it on my 6" APO turns it into an f/12 scope..

It is because dobs start so fast that even with some kind of OCS, you can still get lower power, wider fields than with many other instruments even with much smaller aperture.

It really is the best platform to binoview, and especially with Bintotrons or Denks (or similar).

This is because for larger SCTs, the high power arm often simply gives too much power for seeing.

With a Binotron in my 12" using D21s, I would have 91x, around 160x or so, and about 210x or so (I forget the exact numbers) and this works out to a very decent low, mediumn and hig powers.

In the C14, even with the D21s, I would be stuck at 370x, which simply is far to much apeture.

Most DSOs won't fit into the fied, and it is too much power for planets. So, you use the straight thought mode, but that is often not quite enough, so you wind up changing eyepieces, which defeats the purpose of having a high power switch.

I found less value in the Binotron when used on the C14 than when using on the dob. Far less value. In fact, I swapped out for a 41mm Pan very often.


With the Dob, I have almost as wide a field with the Mark Vs and 1.7x GPC as I had with the C14 using a 41mm Pan!!!


And that is the penalty you get with a BV in an SCT... An even smaller field than with monovision.

There is almost always some compromise with BVs.

Even in refractors that don't need OCS, you are still limited to 1.25" eyepeices, and in a refractor, for me, that denys you the one use where these scopes truely are untouchable, which is wide field viewing... You simply take that away...

#10 Sarkikos

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Posted 17 October 2013 - 08:48 AM

Unless you can reach focus without a GPC, using them in a refractor seems like such a waste to me.

For me, the only place were refractors are truely superrior is in their ability to present wide, coma free, well illuminated fields of view.


Exactly. Unfortunately, it appears that many - most? - refractors require that the tube be shortened in order to come to focus natively with a binoviewer. Get out your saw! :grin:

Mike

#11 Sarkikos

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Posted 17 October 2013 - 09:00 AM

The major problem that I've seen out-of-the-gate for binoviewing SCTs, is that even though they often have enough back-focus for native magnification, that focus setting will probably bring you out of the diffraction-limited range of the SCT. The corrector plate is designed to correct for spherical aberration only within a certain range. Move the focal plane beyond that range, and you risk inducing SA. Not too good, especially for higher power planet/lunar observation.

Setting up an SCT to bring it closer to or within the diffraction-limited range of the corrector is possible with some scopes and binoviewers, but only with the addition of special - often expensive - adapters and diagonals.

Mike

#12 REC

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Posted 17 October 2013 - 09:14 AM

Hey Ed, just a quick note, I am able to get both of the double star clusters in my FOV of my 10" Dob with the reducer arm in with the Denk and 20mm SWA EP....quite pretty!

Bob

#13 tonyt

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Posted 17 October 2013 - 06:23 PM

I like using the Binotron in my 5" refractor for moon and planets, but my skies often don't allow me to go to higher magnification where a larger aperture can stretch it's legs. I almost exclusively use larger scopes for deep sky, although I occasionally get the chance to point one at a planet when a lazy summer high pressure system is sitting overhead.
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