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Comparison TV and Denk standards

Started by tomhole, 09/30/2003 10:07PM
Posted 09/30/2003 10:07PM Opening Post
Had a nice night for doing some testing and had some impressions that I wanted to share. Nothing revolutionary, just some ramblings. Seeing 4 of 10. Transparency good, could just make out the Milky Way. 10" f/4.7 Orion XT10.

The best view of the night was the 24 Pans in the binoviewers in the 80mm refractor. 23x and a 3 deg TFOV. If there were some way to get that with a 10 inch or larger scope, I would hafta pull out the credit card straight away.

On to the important stuff. TV binovue vs Denk standards. I used my GTO zooms to take care of the difference in magification bewtween the TV with 2x corrector and Denk with 1.37x 2" OCS. The GTO zooms had markings for 7.4mm and 11mm. This just happens to match the two systems up nicely. I got 228x in the TV's and 222x in the Denk standards.

Nothing of interest on the double double.

M57 looked the same in both. A star just above M57 was a good test for light throughput. I could see that star just a little easier with the Denk standards than the TV. It was a very slight difference, but I verified it 3 times.

M13 was a draw. A darker sky may have revealed a winner, but not tonight. Looked wonderful, btw.

M31 and it's friends. A draw.

Mars. Slight edge to the TV's. I spent a lot of time here as the seeing was average with occasional excursions to above average. Overall, I could see a little more detail in the TV than the Denk standards.

I discovered an issue with the Denk ep holders while messing with the zooms on Mars. The Denk ep holders are great at getting the ep centered when you tighten them up, but I could wiggle the ep in the holders even after I had them cinched down as tight as I could. Wiggling the ep at this power quickly unmerged the image. All I had to do was loosen the holder and tighten it back up to let the self-centering action do its thing. Until I figured this out, I had a few minutes of cross-eyed viewing. I tried all of my ep's and all of them would wiggle in the ep holder after being tightened down. Are the ep holders on the Denk II (non diopter) the same as the Denk I?

The TV ep holders held the ep solidly. I could not wiggle any of my ep's. The TV holders are also deeper so my longer barreled ep's would seat all the way to their shoulder.

Not a big deal, but something to be aware of.

One thing the Denk standards could do that the TV could not: 1 deg TFOV in my 1200mm focal length dob. Best the TV could muster was a .65 deg TFOV. That makes a big difference for deep sky work. Big enough to cause me all kinds of problems with regards to where I go from here. I tried the 2" OCS on the TV's, but without a better adaptor, the 2" OCS protrudes into the light path when at focus. That won't do at all.

cont'd
Posted 09/30/2003 10:09PM #1
So, I'm going to draw a whacky conclusion after only one night of casual comparison. The Denk standards are so close to the TV binoviewers on deep sky stuff that I could not tell the difference in a double blind Pepsi challenge. I would give a slight edge to the Denks in light throughput and a slight edge to the TV's in contrast. Both were equally sharp. For Mars (I say Mars because I haven't compared them on the gas giants or the moon), I have to give the edge to the Televues. This is all my opinion and based on my equipment. I don't think this is a very controversial conclusion as it seems to match what many observers have reported.

If you held a gun to my head and made me choose, I wouldn't. You'd just have to go right ahead and shoot me. The TV gave a slightly better view of Mars but that .65 deg max TFOV is a deal breaker for me.

If your lookin' to buy a binoviewer, I'll let you draw your own conclusions. Different strokes for different folks.

Hope this wasn't too long and boring. I also hope someone found the information useful. If not, I still have my day job wink

Clear skies,

Tom

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