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Viewing 1 to (6 Total) Eye Pieces |
littleken
Total Posts: 7
Joined: May 12, 2016
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Hi Gordon,
Here a list of eye pieces that I plan to use along with a TV Parra Corr Type II. I want to make sure there won't be any focusing issues.
TV 35 mm Pan 2" barrel
TV 22 mm Nag 2" barrel (my all time favorite)
TV 12 mm Nag1 /4 & 2" barrel
TV 9 mm Nag 1 1/4" barrel
As you can see I'm partial to Tele Vue and I do have more.
I also have a set Baader Hyperion 24 mm to 3.5 mm that I use for out reaches.
What do you think?
Thanks,
Ken
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Posted on June 04, 2016 at 11:26 AM
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gordon
Total Posts: 31
Joined: June 24, 2013
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Re: Eye Pieces
Hi, Ken,
I have the 22mm myself, and I have used the Baader in other Renegades. I'll look up all the specs on the rest of the batch, and make sure that I get the Renegade focal plane set correctly. Given the 22mm, it should just be a matter of checking for relative position, and making sure the whole set fits within the envelope. Are you planning to use a Barlow? Sometimes they are a little trickier. Also, I can include an extra focuser plate so you can vary the focal plane position yourself if need be. It is pretty easy to take off the focuser and mounting board, and replace the mount with the different thickness board. No problems this way!
Gordon
Posted on June 04, 2016 at 9:52 PM
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littleken
Total Posts: 7
Joined: May 12, 2016
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Re: Eye Pieces
Gordon,
What's the max power you feel you scope can go to? With the use of the Parra Corr the four TV E/p's listed should have a power of 55X to 215X. The 3.5 Baader hits 551X . At this time I do not plan on using a Barlow (I do have a 2" Powermate). I do know about putting plates under the focuser. I've done that for my old 12.5. We had a great star party here, your scope would have been the second biggest here. Forty people Friday night, over sixty Saturday. Our club has a 22" dob.
For super power I have TV 3-6 mm Nag Zoom.
Later,
Ken
Posted on June 05, 2016 at 10:38 AM
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gordon
Total Posts: 31
Joined: June 24, 2013
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Re: Eye Pieces
Hi, Ken,
The issue of magnification with very fast mirrors is opening up some interesting questions. There are some eyepieces that just don't work as well with an f/3.0 mirror as they will with an f/5.0 mirror. Poorly-designed or cheap eyepieces are likely themselves to show 'stig, as the fast mirrors bring this out. You might have to test this by trial and error! Mainly, this is about eyepiece design and performance. With the eyepieces you list, those that cover up to 215X should not be a problem. But that 3.5mm eyepiece may be a disappointment to you. I had a set of Hyperions that I bought for a client. On an f/4.5 mirror, the wide eyepieces were all great, and a 10mm was acceptable. But the 5mm I tried was very poor. When compared against an Ethos, the Ethos was the winner hands down. Of course there is a huge difference in price there, but the point is that the design of the eyepiece was the make-or-break factor at that magnification. And it's not just the manufacturer, either. I have a 4.6mm from TeleVue that I seldom have any fun with. Don't know why, but a Barlow on another longer eyepiece gives me better views than the native 4.6mm.
You also have to consider the effect of the shorter focal length. If you put a 5mm eyepiece on a 20" f/5 mirror, you will get about 500X. But on a 20" f/3 mirror, that same eyepiece yields only about 300X. So you can see that the f/3 mirror has to be figured to considerably higher standards in order to give comparable magnification. Or you will need a shorter, and more expensive and better-designed eyepiece to achieve the same magnifications. Frankly, that is why most opticians won't make an f/3 mirror for you, or at least not for any reasonable price. Ken, your f/3.3 mirror is a little more forgiving than an f/3.0 mirror, but I still wouldn't expect too much from the 3.5mm Hyperion. The interesting thing would be to test the 3.5mm against something like a 4.7mm Ethos. To achieve highest magnifications, the eyepiece becomes a very important component in the system! My effort with any mirror is to make it as good as possible, and to make sure the primary mirror isn't the limiting factor!
Thanks!
Gordon
Posted on June 06, 2016 at 1:59 PM
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littleken
Total Posts: 7
Joined: May 12, 2016
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Re: Eye Pieces
Gordon,
I totally agree and understand your last post. The four TV E/P's 35 mm to 9 mm are/will be the main range that I plan to use. I normally use the Baader 24 mm, 21 mm and 17 mm for outreaches. I only use higher power if what to try to see something tighter, I will make do with what I can get. I also have a Ethos 13 mm which I'm very carefull with, I don't let too many people touch it. I do agree that Baader 5 mm and 3.5 mm are limited.
I normally use the 35 mm to quick find then switch over to my favorite 22 mm for detail viewing. If I want more detail I'll go to the 12 mm, I will rarely use the 9 mm.
The Fedex guy said no packages today,
Ken
Posted on June 06, 2016 at 5:44 PM
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gordon
Total Posts: 31
Joined: June 24, 2013
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Re: Eye Pieces
I have that same 22 mm, and I just love it. It is a great general purpose eyepiece. The moon is just crazy with it. And I find that it is very good for wide-field objects that aren't too big. Open clusters are excellent. One of my guilty pleasures is my Tele Vue 31mm Nagler. With my 20" f/3.0, the view of M31 and companion galaxies is just superb. All three of the showpieces fit in the same field. The Double Cluster in Perseus is another spectacular object with the "pineapple". You will have to calculate the exit pupil on your 35 mm. Even if it is technically a little too big, I'll bet you get some good views. The only trick is, on the F/3.3 your secondary is pretty big. Some eyepieces will give you some shadowing with it, so you really need to get your eye placed just right behind the eyepiece. Can't wait to start testing your 20". I know it's going to be fun!
Thanks,
Gordon
Posted on June 06, 2016 at 10:02 PM
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