Posts Made By: Chris Gorman

I have a 10" dob and I'm looking to get a Denk II with 2" OCS. Assuming I get two 24mm Pans and two 16mm Naglers, I will have(using the 1.3x and 2.5x for the OCS):

24mm Pans - 18.5mm(1.3x) and 9.6mm(2.5x)

16mm Naglers - 12.3mm(1.3x) and 6.4mm(2.5x)

So my focal lengths will be 18.5mm, 12.3mm, 9.6mm, and 6.4mm, correct?

What about wide-field low power views(say around 26mm-32mm focal length ep's), is this possible with binoviewers? Or am I going to have to go mono-view for low power wide-field views?

I'm piecing together a 10" f/4.8 dob. I'm thinking about installing a Feathertouch focuser but I don't know which one to get. They offer 1.5", 2", and 2.5" travel versions. I'm interested in using a binoviewer as well so I don't know if that effects how much travel I need. Do you just pick the one with the most travel, or is it more complicated than that?

Also, does anybody know a good website that shows how to install and square a focuser? Thanks

I need a laser collimator and want some advice on which one to get for a 10" dob. I did have an Orion(which was about 2 years old) but threw the thing away because the laser wouldn't hold alignment. Are the new Orion laser collimators any better, or should I just forget about them? The EZ Telescope and Kendrick lasers seem pretty good, any opinions on these?

I have a 2" focuser, will a 1 1/4" laser be less accurate than a 2" laser because of focuser slop? Basically what I want to know is should I get a 1 1/4" or 2" laser collimator?

Oh man, where do I begin. Ok, I just ordered a 10" F/4.8 dob. This will be my second scope, so I don't have much experience. I asked for a 1 1/4" focuser because I haven't decided which 2" focuser I want(FeatherTouch, DX1, DX3, etc.). This week I will finally be able to test out a FeatherTouch. So I figured that after I receive this new dob I would have to do some modifications to it. So here are my questions, and there are many:

1. If I go with the 2" FeatherTouch focuser, is this going to screw up my focal length? Or are 1 1/4" focusers generally the same height as 2" low profile? Am I going to have to move the primary back a little bit away from the secondary? I don't know the height of the 1 1/4" focuser as I haven't received the scope yet.

2. When you are setting the distance from the diagonal to the focal plane, how far out do you rack the focuser? In other words, if I have a FeatherTouch with 2 inches of travel, do I rack it out 1 inch and use that distance? That way I will have one inch of out-focus and one inch of in-focus from the focal plane. Following the same logic, if I had a 2" focuser with 3 inches of travel I would rack it out 1.5" when I go to set the distance. Or is that not correct?

3. Am I doing this correctly? Given these figures: 10" f/4.8 dob with a 12" ID tube, a focuser height of 1.6"(FeatherTouch specs) with 2 inches of travel, and a tube thickness of 1/4", my distance from the diagonal to focal plane should be set at 8.85". 6"(radius of ID of tube) + 1/4"(tube thickness) + 1.6"(focuser height fully racked in) + 1"(middle of travel distance for focuser) = 8.85"

4. I will be using Naglers and Pentax ep's in my scope, as well as a Denk II binoviewer. If I go with the FeatherTouch, which travel length would you recommend? They offer 1.5", 2" and 2.5".

Thanks in advance to anybody who tackles all of these questions.

I'm looking for a premium focuser for a 10" dob. I would like the opinions on these two focusers. Now, I already know that most people love the FeatherTouch. Please, only respond if you have used both focusers or if you have used a Clement focuser. I'm looking for comparisons between these two focusers as well as comments about the Clement focuser.

I'm aware that the owner of Clement focusers reads this board. But I ask that you not chime in as I'm looking for unbiased responses. Thank you for understanding.

Ok, I need some of you really smart people to help me. I'm running into design issues here. Here are the facts: 10" f/4.8 dob which will be used for visual observing only. I enjoy observing DSO's more than planets, but still like looking at the planets. FeatherTouch focuser, using 2" Naglers and new Pentax XW's. Also probably a Denk II binoviewer.

I've run all sorts of scenario's using the different size secondary mirrors and I think I need to go with a 2.6" secondary. When I ran the dimensions through NEWT it said there was "vignetting at focuser of 75% ray". Everything else was ok. Is this a big problem, or is it no big deal? I increased the focuser diameter by just .05" and the vignetting went away. So obviously it's just barely off.

I don't really understand this 75% and 100% zone ray concept. Can somebody explain it to me? It seems like all that should matter is the "On-Center" rays.

Do you think a 26% obstruction is really going to hurt my contrast? I could go with a 2.14" secondary(21% CO) but the FIF would be below .5". This wouldn't be a good idea, right?

I need some advice here. I want to buy a nice low power ep for a 10" f/4.8 dob. The 31mm Nagler seems like the obvious choice, but there are two other ep's that I'm considering. Those being the new 30mm Pentax XW and 26mm Nagler. The difference in price between these three ep's is not that great, so don't base your response on price. What I want to know is which one of these performs the best when it comes to sharpness to the edge, contrast, etc.

I'm looking to buy a few of the XW's in the mid and high power range. Has anybody looked through these yet?

I'm thinking about putting a different color varnish on my telescope base. The base is made of plywood, can I just sand the old varnish off with sand paper? Will that harm the plywood? Or should I just use some type of solvent to strip off the old varnish? Sorry if this is a dumb question, but this is my first "wood-working" experience.:')

I'm in a little bit of a conundrum. I'm putting together a 10" f/4.8 dob and I need a secondary mirror. I have been told that I should try and obtain a 100% fully illuminated field of .5". I have also been told that the central obstruction should be kept to a minimum. This is where the problem is, I can't have both. A 2.14" secondary only gives me a 100% FIF of .36". It does appear though that the drop off is gradual. In other words 100% FIF is .36", at .67" the illumination drops to 94% at the edge. Not a big change. A 2.6" secondary gives me a 100% FIF of .93"(overkill really). Of course the 2.6" will give me a central obstruction of 26%.

I will be using a binoviewer, so my main ep focal lengths will range from 4mm-17mm. If I understand the concept of all of this correctly, using a 2.14" secondary would be fine because even a 17mm ep would still have 94% illumination at the edge. BTW, if I go with the 2.14" secondary the barlow of the binoviewer will protrude into the lightpath of the primary mirror by about a half inch. If I go with the 2.6" I can fix this problem, plus have a larger FIF for my 31mm Nagler. What would you do?

After I posted this message I checked out the specs again on NEWT. When it tells you the 100% FIF, let's just say it's 15mm, does that mean that a 15mm ep will be 100% fully illuminated, or does that mean a 15mm field stop? If it's the field stop then I misunderstood the concept above.