scopemobile
Member
Posts: 99
home town/country: Glasgow/Scotland
|
Post by scopemobile on Jan 11, 2016 22:47:16 GMT
has anyone thought of the feasibility of fitting a bullet type video camera[lodestar @ 32 mm dia] in the area of the secondary mirror of reflectors,dobsonians ,etc,to by pass the 45 degree mirror which i read somewhere is 90 percent efficient, a year or two ago shevill and rick were discussing a top secret telescope project , is this it? john.
|
|
|
Post by Dragon Man on Jan 12, 2016 6:19:42 GMT
Yes John, it has been done by several people in the past. But the idea seems to have lost momentum. Not sure why.
It's a wonder some clever company hasn't manufactured a 'camera holding spider' for reflectors.
|
|
|
Post by davy on Jan 12, 2016 8:27:00 GMT
Bit like the hyperstar idea
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jan 12, 2016 19:08:05 GMT
Distance from the mirror to the eyepiece includes the distance from the mirror to the diagonal and from the diagonal to the eyepiece. You would have to extend the tube or as they do with hyperstar, design a lens to compensate. At any rate what you are talking about is called a Schmidt Camera. en.wikipedia.org/wiki/Schmidt_camera
|
|
|
Post by Rick in NWArk on Jan 15, 2016 18:58:09 GMT
Yes, we've discussed this idea in the past and its still in my head. To be most effective, you really need a focusing solution so that you can introduce focal reduction and move the camera in and out to hit focus. The problem with Schmidt Camera designs are field curvature and fixed focal planes. If you want to have a single-use solution (one specific field of view / camera), no problem.
One of these days I'll buy a cheap mirror and play around.
|
|
|
Post by davy on Jan 15, 2016 20:56:09 GMT
On the phone to uncle john tonight,there are a few hurdles that can be overcome,first up is the scope.i believe a skywatcher truss dobsonian would be my scope of choice of course I would want the goto version. Now at £800 for an new 8" it's an expensive experiment. Reason why ..the focal length can be adjusted by the truss rods ,so this can sort out focal issue. Next part was mounting the camera.. The spider vane from the skywatcher would be easier to source. Problem that may arise is the modified camera holder it may be to heavy for the vanes. Heat from camera will it be an issue??. Best option would be a new manufactured front spider camera holder. What you do when bored lol
|
|
scopemobile
Member
Posts: 99
home town/country: Glasgow/Scotland
|
Post by scopemobile on Jan 16, 2016 2:07:42 GMT
davie and ldb mentioned hyperstar, i looked on the web , made by starizona for celestron and a couple of meades. how is f10 to f2 accomplished ? [well above my level] .mallincan is said to be compatible. has anyone broadcast with this setup or is the fov too narrow. it seams to take slr's, a large footprint for incoming light, the price is quite heavy. john.
|
|
|
Post by davy on Jan 16, 2016 14:24:08 GMT
To push this idea on I have a 8" Newtonian telescope that uncle john can have to experiment on..if he accepts the misson..lol. Have thought about the focal issues and how to adapt this steel tube to accept a camera mod,had initially thought on truss scope as an option.my thoughts on steel tube adaption. The tube would get slots made in it to allow the spider vane to travel length wise down the tube to achieve focus.
|
|
|
Post by Rick in NWArk on Jan 17, 2016 17:10:48 GMT
davie and ldb mentioned hyperstar, i looked on the web , made by starizona for celestron and a couple of meades. how is f10 to f2 accomplished ? [well above my level] .mallincan is said to be compatible. has anyone broadcast with this setup or is the fov too narrow. it seams to take slr's, a large footprint for incoming light, the price is quite heavy. john. The hyperstar is designed for the specifics of the Schmidt-Cassegrain design -- where the large primary is an f/2 mirror and when the light goes back up the tube to hit the secondary - the secondary takes it to f/10 shooting it back down the tube thru the hole in the primary. The hyperstar allows you to get that f/2 image from the primary only. Look for Jack Huerkamp's videos on YouTube - he has a lot of excellent examples of using Hyperstar
|
|
|
Post by ChrisV on Jan 18, 2016 3:00:56 GMT
I had a look at the hyper star for my sct. But it costs a fortune - cheaper to buy a dedicated 2nd scope?
Chris
|
|
|
Post by Rick in NWArk on Jan 18, 2016 22:24:59 GMT
Yeah, its pricey but you get a lot of photons with a Celestron 11", even with the hyperstar+camera obstruction...
Me, I'd probably drop it into the corrector glass and ruin my scope!
|
|
|
Post by davy on Jan 22, 2016 15:30:28 GMT
Thats unc john picked up the 8" Newtonian scope for the experiment.. focusser removal and make up a new spider to take a camera.. looking for input and suggestions lets make it a forum project.
|
|
|
Post by Dragon Man on Jan 23, 2016 13:55:05 GMT
How will it focus davy?
|
|
|
Post by davy on Jan 23, 2016 17:02:39 GMT
Two possible ways ken.a new spider vane will be made like a sleeve fit,it will slide down tube on slots,other thought was to adapt the focusser to spider and adapt it for focusing..if it all goes pearshaped will make a new skeleton body and take it from there.I dont use the 8" anymore so nothing ventured nothing lost..unc john is a engineer and a dab hand at metal work..whats folks thoughts on the project
|
|
|
Post by Rick in NWArk on Jan 24, 2016 2:08:23 GMT
That second solution was what I had in mind, Davy. My old Coulter 8" has a friction fit focuser that looks like this: Usually its the first thing to get replaced -- usually with a rack & pinion focuser. But in our case we want something more like this old thing -- it has a much smaller obstruction profile. It was something like this or a heliacal focuser that I was thinking of using.
|
|
|
Post by Dragon Man on Jan 24, 2016 9:16:16 GMT
Helical focusers are good because of their small footprint in the light path. Really high quality Borg 1.25" & 2" Helical focusers are available from Hutech at reasonable prices. I had to buy a 2" one to replace one I broke, and it was only $120 (60 pounds). www.sciencecenter.net/hutech/borg/focuser.htm
|
|
|
Post by davy on Jan 24, 2016 9:52:55 GMT
Unfortunately its a rack and pinion focusser,but maybe able to use internals to make a workable test piece.
|
|
|
Post by Rick in NWArk on Jan 25, 2016 14:17:50 GMT
Absolutely Davy -- for a proof of concept you could even stick a robo-focuser on there
|
|