Click here if you are having trouble logging into the forums
Privacy Policy |
Please read our Terms
of Service | Signup and
Troubleshooting FAQ | Problems? PM a Red or a Green Gu.... uh, User
aa5te
Genial Procrastinator
Reged: 08/30/08
Posts: 429
Loc: Clinton, TN
|
|
I'm posting this here as I think it's good beginner info for those with dobs.
I took my 10" dob out last night for a session. The scope went from inside at around 70F, to outside at about 45F, with no cooldown period. In the summer, this isn't too much of a problem, as we keep it about 70F indoors, and it usually about 70-75F when I take it out. Jupiter was still above the trees, so I dialed it in first as it would be out of sight within a few minutes. Disappointment sets in - can't focus the moons, no banding visible, lots of glare - I just collimated this thing! Tried the other eye, same story. Wait, idiot, I forgot to turn the fan on, so I crank it on high. Within 10 minutes, all of those problems disappeared and the bands were clearly visible, almost just as good as they are in my classic refractors (definitely needed more cooldown time, but the trees ate Jupiter).
So, for planetary viewing or star splitting, a fan really helps out. I've got mine set up with a baffle in the tube that directs air right across the mirror to remove the boundary layer of air (thus helping out with the views). I made mine for about $10 - details and a link to some pics are in this thread:
CN thread on fans
--------------------
Shane
Binos: Apogee 25x100 / Burgess Optical 25x100 / Pentax 20x60 PCF WP / Tasco InFocus 10x50
Tripods: Sunpak PlatinumPlus Ultra 7500TM / Quickset Samson
Refractors: Meade DS-2102AT-TC 102mm f/7.8; Sears Discoverer 3 (4454) 80mm f/15; Jason 313 Discoverer 60mm f/15.2
Reflectors (Dob): Hardin Optical DSH10 10" f/5
EP's: Zoom: Zhumell 8-24mm & Circle K 7.5-22.5mm 0.965"; 9-52mm Plössls; Zhumell 2x barlow
Kodak Z760; Orion SteadyPix camera mount; Orion LaserMate Deluxe Collimator
|
RonBurgundy
sage
Reged: 06/16/09
Posts: 271
Loc: Philadelphia
|
|
I think that this is also an important post for folks with SCTs as well. I don't have a fan, but I leave my scopes in the car (with a SERIOUS security system, along with lojack ) for a few hours before I head out and observe. I'm currently looking into one for my scope. That's a great post. I think that it also helps in DSO observing, though some may disagree. As much as I love my ACHRO, a cooled scope is kind of like the difference between a (similarly temperatured) APO and ACHRO. it does make a difference for all viewings. Thanks for this!
--------------------
Kipp Ginsburg
8" LX200-ACF
Orion 120mm F/5.0 Piggybacked Refractor
Meade UWA Set [4.7mm-30mm]
DSI-II
Edited by RonBurgundy (11/08/09 01:10 AM)
|
Sky Captain
Metal Whisperer
Reged: 11/07/04
Posts: 7195
Loc: Issaquah, WA.
|
|
Quote:
I forgot to turn the fan on, so I crank it on high. Within 10 minutes, all of those problems disappeared and the bands were clearly visible,
It truly is an important part of the viewing experience. With the purchase of my first dob a few years ago, I always had to set up and let the thing cool for an hour before the stability of the optics made it usable. Alot of times I don't have that much time to wait before a viewing session can be cut short.
The stock fan is a 3" on the 12" LB and I found that the hole in the center of the cell was 3.5", so I replaced the fan with a larger 3.5" and added a clear plastic cover to direct more air flow through the back of the scope and around the mirror.
This was a HUGE difference, and now I can be doing some decent viewing after only 20 minutes of cool down and it only gets better from there.
--------------------
Equipment Overload!
Kerry
|
SteveG
sage
Reged: 09/27/06
Posts: 238
Loc: Seattle, WA
|
|
Hey - mine is similar (stock fan, 10" LB)
--------------------
WO Megrez 110 ED on SP Mount
10" Meade LightBridge
Orion ED 100 on Polaris Mount
6" f8 Edmonds reflector on GP Mount
4.5" F8 Orion EQ Reflector
Astroscan
Meade 226 2.4" f11.7
|
joelimite
sage
Reged: 09/01/08
Posts: 235
Loc: Fayetteville, AR
|
|
Those fan mods look terrific. I would love to see some pictures of what kinds of fans people are using on the XT line of Orion Dobs (hint, hint:)
I've simply been taking a house fan out with me, plugging it into the exterior outlet behind my house, and aiming it at the mirror. However, I need a more elegant solution for when I trek to a dark site. I know Orion offers an add-on fan accessory, but I would love to see how other people have added fans to their XT Dob.
--------------------
Orion XT8 Dob w/ Moonlite 2-speed Crayford focuser, Vixen A80MF w/ GSO 2-speed Crayford and Porta Mount
32mm Televue Plossl, 31mm Hyperion Aspheric, 24mm Meade SWA, 17,13,8mm Hyperions, 6,5,4mm TMB Planetary, 5mm Baader Genuine Ortho
Garrett Optical 20x80 UL Binoculars, Nikon Action Extreme 10x50 Binoculars
|
Achernar
Postmaster
Reged: 02/25/06
Posts: 5028
Loc: Mobile, Alabama, USA
|
|
What in the world are all those cylindrical objects on the rear of your optical tube assembly? Are they some sort of counterweights?
Taras
--------------------
15-inch F/4.5 Dob under construction
10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
A whole bunch of eyepieces, filters and other accessories....
Two curious cats
|
hudson_yak
Pooh-Bah
Reged: 11/15/07
Posts: 1106
Loc: Hyde Park, NY, USA
|
|
Low-tech, ugly, but still functional variation:
In answer to the later question, yes, the round things are counterweights. The LB needs quite a few, I have to add another one (1 lb) to balance the cotton shroud I just got.
Mike
--------------------
Meade 8" LX10
Orion ED100 + Losmandy GM-8 + Berlebach UNI 24
Meade 12" LightBridge
|
Sky Captain
Metal Whisperer
Reged: 11/07/04
Posts: 7195
Loc: Issaquah, WA.
|
|
Quote:
What in the world are all those cylindrical objects on the rear of your optical tube assembly? Are they some sort of counterweights?
Taras
Yep, those are CW's. I designed and machined them several years ago when I found that a 35mm Stratus, a 8x50 RA finder and a telrad made the front of the scope a "little" heavy. The three main studs/weights serve to act as a stand to protect the collimation bolts and I made three CW's to slip over the studs for extra weight where needed to keep the proper balance.
Here is an early shot with the weights not installed.
--------------------
Equipment Overload!
Kerry
|
nobody special
sage
Reged: 12/30/08
Posts: 405
Loc: Connecticut
|
|
Quote:
I've simply been taking a house fan out with me, plugging it into the exterior outlet behind my house, and aiming it at the mirror.
A classic example of why I love this forum so much. I never would have thought to do that.
I too need a fan, I was thinking of using one of the old CPU fans I have laying around, not sure it would work though.
--------------------
Tom
Orion XT8 Classic
Hyperion 13mm (With 28mm Tuning Ring)
Orion Sirius 25mm
Meade Series 4000 Plossls 32mm 6.4mm
Orion Shorty Plus 2x Barlow
Telrad
OPT OIII Filter
ND Moon Filter
80a Blue Filter
Smart Seat III
|
Jeff Chappell
member
Reged: 08/05/09
Posts: 16
|
|
Quote:
Those fan mods look terrific. I would love to see some pictures of what kinds of fans people are using on the XT line of Orion Dobs (hint, hint:)
Here's the Orion fan on my old-style XT10. This is the model with the metal plate behind the mirror cel. I used a hole saw to cut a hole in the plate, then mounted the fan directly to it. I don't notice any vibration with the fan running, even at higher mags. But I usually turn it off anyway as soon as the tube currents subside.
--------------------
Jeff Chappell
Member, Oklahoma City Astronomy Club
Orion XT-10
|
joelimite
sage
Reged: 09/01/08
Posts: 235
Loc: Fayetteville, AR
|
|
Thanks for the pic, Jeff. That looks great. Perhaps I'll pick up the Orion fan after all.
--------------------
Orion XT8 Dob w/ Moonlite 2-speed Crayford focuser, Vixen A80MF w/ GSO 2-speed Crayford and Porta Mount
32mm Televue Plossl, 31mm Hyperion Aspheric, 24mm Meade SWA, 17,13,8mm Hyperions, 6,5,4mm TMB Planetary, 5mm Baader Genuine Ortho
Garrett Optical 20x80 UL Binoculars, Nikon Action Extreme 10x50 Binoculars
|
|
18 registered and 6 anonymous users are browsing this forum.
Moderator: desertstars, werewolf6977, ClownFish
Print Thread
|
Forum Permissions
You cannot start new topics
You cannot reply to topics
HTML is disabled
UBBCode is enabled
|
Thread views: 466
|
|
|
|
|
|
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: 