Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

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

Equipment Discussions >> Reflectors

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | >> (show all)
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Thermal Issues and Fans Successes new [Re: Project Galileo]
      #5606666 - 01/05/13 01:50 PM

Project Galileo,

Quote:

...added a Mauro Da Lio baffle...




Here is an interesting quote from that thread:

Vortex

Quote:

In a tube, a rear fan also creates a vortex which scrubs and lifts much of the boundry layer away too.

At least it does in my 10" f/5.




So that vortex I saw in the defocused image through my 8" f/6 Dob might be a good thing? Perhaps it needs to be modified or enhanced somehow to improve its effectiveness.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Thermal Issues and Fans Successes new [Re: nevy]
      #5606671 - 01/05/13 01:53 PM

nevy,

Quote:

That looks like it could be very usefull as I have two scopes with fans so it could be used on either scope to mess with the fan speeds , it would save the trouble of fitting pots to both scopes , come on spill the beans where do you get such a device :-).




Exactly. The less after-market cutting, splicing and wiring I have to do the better!


Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
MessiToM
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Huntingdon PA
Re: Thermal Issues and Fans Successes new [Re: Sarkikos]
      #5606705 - 01/05/13 02:10 PM

This thread has got me cruising for fans. Check out this 110cfm fan at "low" rpm even
http://www.frozencpu.com/products/13819/fan-901/Akasa_140mm_x_25mm_VIPER_PWM_...

$9 4 fan controller!
http://www.ebay.com/itm/4x-Port-FAN-SPEED-CONTROLLER-3-5-Bay-Black-Aluminum-P...

Edited by MessiToM (01/05/13 02:15 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
MessiToM
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Huntingdon PA
Re: Thermal Issues and Fans Successes new [Re: MessiToM]
      #5606729 - 01/05/13 02:29 PM

O guys..........now I have a new project..

Post Extras: Print Post   Remind Me!   Notify Moderator  
MessiToM
scholastic sledgehammer
*****

Reged: 12/21/09

Loc: Huntingdon PA
Re: Thermal Issues and Fans Successes new [Re: Sarkikos]
      #5606743 - 01/05/13 02:39 PM

Quote:

nevy,

Quote:

That looks like it could be very usefull as I have two scopes with fans so it could be used on either scope to mess with the fan speeds , it would save the trouble of fitting pots to both scopes , come on spill the beans where do you get such a device :-).




Exactly. The less after-market cutting, splicing and wiring I have to do the better!


Mike




I use something similar for dew busting. Its just a 12volt cigarette adapter with variable voltage outputs. Mine was from radioshack


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Thermal Issues and Fans Successes new [Re: MessiToM]
      #5606765 - 01/05/13 02:52 PM

I'll have to start looking for those. There are a lot of neat off-the-shelf gizmos in the 12-volt Universe!

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Thermal Issues and Fans Successes new [Re: Scanning4Comets]
      #5607630 - 01/06/13 12:38 AM

Quote:

Detail on Ganymede.

Bionic eyes?




Not at all. At least 8/10 seeing and preferably about 400x though you can see it with less. It's an uncompromising kind of feature that demands a steady image. I've tried with 7/10 which is still good seeing but its too soft at the magnification needed to show some albedo here.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scanning4Comets
Markus
*****

Reged: 12/26/04

Re: Thermal Issues and Fans Successes new [Re: azure1961p]
      #5607719 - 01/06/13 02:50 AM

I'll give it a try, LOL! Maybe I'll get lucky and see the footprints on the moon too.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: Thermal Issues and Fans Successes new [Re: Scanning4Comets]
      #5607752 - 01/06/13 03:57 AM

Quote:

Maybe I'll get lucky and see the footprints on the moon too.




If you do, report back. I wanna try it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Thermal Issues and Fans Successes new [Re: azure1961p]
      #5607943 - 01/06/13 09:27 AM

Pete,

Quote:

Quote:

Detail on Ganymede.

Bionic eyes?




Not at all. At least 8/10 seeing and preferably about 400x though you can see it with less. It's an uncompromising kind of feature that demands a steady image. I've tried with 7/10 which is still good seeing but its too soft at the magnification needed to show some albedo here.




I've caught albedo features on Ganymede during excellent seeing but have never seriously tried to tease them out, much less attempt a drawing. That probably requires higher magnification than I like to use on a scope that does not track.

But I have gone up to 600x for Mars when it was at about 6 arcsec just to see what could be seen, and had good results. Didn't attempt a drawing, though. Ganymede is appreciably smaller at about 1.5 arcsec. So Ganymede's apparent diameter is about 4 times smaller than Mars when I was viewing that planet. With steady seeing, though, I should be able to tease out gross albedo markings.

I always resolve the Galilean Moons as disks. That is no problem for a decent 10" Dob.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scanning4Comets
Markus
*****

Reged: 12/26/04

Re: Thermal Issues and Fans Successes new [Re: Sarkikos]
      #5608242 - 01/06/13 12:21 PM

Of course I can see the moons as discs, as I did during Oct 25th....but to see DETAIL on one of the moons? Gimme a break.

All the power to you.....Something isn't adding up here.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Thermal Issues and Fans Successes new [Re: Scanning4Comets]
      #5608382 - 01/06/13 01:29 PM

Seeing gross albedo markings isn't exactly seeing a lot of detail. You can probably see a lot more "detail" with your naked eyes looking at the Moon than moderate-sized amateur scopes can see on Ganymede in excellent seeing. I don't see this as incredible, but just a big bother to do if you don't have tracking on your scope.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Thermal Issues and Fans Successes new [Re: Sarkikos]
      #5608813 - 01/06/13 04:57 PM

Markus,

It's not unheard of for a good medium aperture scope to pull this off. Here's a link where one (of several) did a drawing of Ganymede details on a recent night of excellent seeing. http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5606142/page...

Too, one observer seemed go do even a little better with a 6" Maksutov.

The key is excellent seeing. I've never pulled it off with 7/10 but 9/10 seeing yes. Also Io if compared to Europa shows a subtle ovular shape, a diffraction effect caused by the brighter equatorial zone versus the dimmer polar regions.

Ganymede s surface features for me need unusually good seeing had here in Connecticut only in the summer. Io tho just 1.2" wide to Ganymedes 1.7" curiously shows the effects of its equatorial zone in just 6/10 seeing.

As far as albedo details on the other moons not counting Io it would seem to be substantially more difficult due to the smaller angular size of the features and inherent lower contrast.

It all adds up - but it takes unusually good observing conditions. And again that's without fans running. I'd imagine the probability now would seem to go up a picketing point or two.

Pete

Edited by azure1961p (01/06/13 05:00 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scanning4Comets
Markus
*****

Reged: 12/26/04

Re: Thermal Issues and Fans Successes new [Re: Bob S.]
      #5611849 - 01/08/13 12:20 PM

Just wondering something here,

Would it be ok to use a 9 volt battery on my 12 Volt fan? I tried it and the fan spins....but I am wondering if the battery will get too hot and malfunction over time?


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Thermal Issues and Fans Successes new [Re: Scanning4Comets]
      #5611861 - 01/08/13 12:25 PM

Quote:

Just wondering something here,

Would it be ok to use a 9 volt battery on my 12 Volt fan? I tried it and the fan spins....but I am wondering if the battery will get too hot and malfunction over time?



The lower voltage reduces the fan speed and the battery won't last more than one night (spoken from experience). The battery won't overheat--it just won't last very long.
The standard "D" cell lasts a lot longer, and 8 of them in series should last several full nights.
However, I use a 12V 8 amp-hour deep-cycle rechargeable for 3 fans, and it needs recharging after one night, so just be aware of the limitations of batteries when running fans. Some 12V fans are small and run fairly slow and consume little power. Others push a lot of air and consume a lot of power.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scanning4Comets
Markus
*****

Reged: 12/26/04

Re: Thermal Issues and Fans Successes new [Re: Starman1]
      #5611875 - 01/08/13 12:36 PM

Thanks for the info Don! I'm going to pick up an 8 "D" cell battery holder and 8 D cells for the fan.

Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Thermal Issues and Fans Successes new [Re: Starman1]
      #5614778 - 01/10/13 12:45 AM

Hi Don, It's De Lorme, If you don't remember I have a old 17.5" Odessey. Do you think 3 39cfm would be enough? I had
planned on putting them in the rear. But after reading that a side one really makes a differance I'm going to put one
on the side to. Do you know of anybody that has a picture
how it should exactly look. You Know every picture tells a
Story!LOL. I had not even considered this option.
I really appreciate you Veterans here on CN pointing me in the right direction. Thanks again! De Lorme


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Thermal Issues and Fans Successes new [Re: De Lorme]
      #5614800 - 01/10/13 01:09 AM

Quote:

Hi Don, It's De Lorme, If you don't remember I have a old 17.5" Odyssey. Do you think 3 39cfm would be enough? I had
planned on putting them in the rear. But after reading that a side one really makes a difference I'm going to put one
on the side to. Do you know of anybody that has a picture
how it should exactly look. You Know every picture tells a
Story! LOL. I had not even considered this option.
I really appreciate you Veterans here on CN pointing me in the right direction. Thanks again! De Lorme



I think 3 fans like that would be fine. One behind the mirror because otherwise heat doesn't dissipate from the rear very well, and two blowing across the mirror.
http://www.fpi-protostar.com/bgreer/fanselect.htm
and
http://www.deepskywatch.com/Articles/rear-fan-newtonian.html
and
here
and
http://www.skyandtelescope.com/howto/basics/3304176.html
and
http://www.atmlist.net/pipermail/atm/2005-August/009756.html
and
http://www.teeterstelescopes.com/images/125casella5.jpg

I'm sure, after that, you should be able to figure it out.
The rear fan should blow directly on glass. I presume you've either replaced or extensively modified your mirror cell by now so that wind on the mirror can actually cool it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
De Lorme
professor emeritus
*****

Reged: 12/30/08

Re: Thermal Issues and Fans Successes [Re: Starman1]
      #5614840 - 01/10/13 02:25 AM

Hi Don, Weather must be bad there to. LOL. Would you place the fans on the side of the tub facing each other or on the same side next to each other? I'm inclined{opinion, educated
guess} that two next to each other in the back and one on the side is better. The reason for one on the side is less air turbulance. Just enough to get the air up the tub.
If I where to put two on the same sides should I put them
where all the air goes right across, or move then down a little so that only 80% goes across and 20% goes acroos the back? Thanks for the advice. BTW,The mirror is washed. I got the base{painted} done with the lazy attached,and setting circles on it.
Tub is sitting on the kithen table{RoseMary is such a great wife} painted inside and out with a color called very black by Valspare. I bought a use heleical focuser that matched with the base plate. Got the digital angle setter today from Sears. Almost done! Once I get the fans I'll be able to drill holes and be finished. Eric told me about the Astro-Fix Locator. Have you or anybody you know used it?
This is so exciting. I really like my CR6" on the CGEM but
I cannot wait to look through this! De Lorme


Post Extras: Print Post   Remind Me!   Notify Moderator  
Bob S.
Carpal Tunnel
*****

Reged: 07/14/05

Re: Thermal Issues and Fans Successes [Re: De Lorme]
      #5614939 - 01/10/13 06:33 AM Attachment (15 downloads)

I have been reading this thread with great interest and thinking back to all of my previous experiments with fans blowing across the front face of telescope mirrors. On a Teleport 14.5" with the "air knife", a 20" Starmaster with Floyd Blue's corner fans and rear blowing fans, Daniel Mounsey's "air knife" on a 12.5" Starmaster, I had very limited success in effectively mitigating boundary layer issues in my steady North Florida skies. There is also the issue of fan vibration that is often not mentioned but some report is a reliable nemesis of our boundary layer solutions.

In my thread on my latest attempt with what we have termed a Comprehensive Boundary Layer Mitigation System (CBLMS), it appears that borrowing successes from of Joe Wambo's front downward blowing fan in his 32" and Jimmy Lowery's 10 enclosed rear MagLev fans in an enclosed rear mirrorbox of his 48" are the only way that I have been able to achieve reliable success in mitigating the boundary layer issues here in North Florida. It involves the use of Magnetic Levitation fans controlled by potentiometers, comprehensive damping with sorbothane, an annulus strategically placed above the primary to create a venturi effect for sucking the air away from the front boundary and out the back of the scope.

The only other really successful application that I have seen for fans is a recent encounter with Dan Kleppner's 10" Starmaster with a rear blowing fan and 4 holes strategically placed above the primary mirror to exhaust the flowing air.

I am hesitant to throw a wet blanket on many of these well-intentioned attempts but my take on it after having experimented for about a decade is that the use of fans is pretty darn tricky in terms of not creating potentially more turbulence or just not having a particulary effective fan system? I also think that location, thickness of the primary and the size of the scope have a lot to do with how effective fans are. Gary Myer's of StellarCat fame had equipped a 30" Newtonian he had with all kinds of different fan systems out in Arizona and was telling me years ago that most of his experiements had not born much fruit. John Pratte of JP Astrocraft that did the design and engineering on my scope also advised that he has had limited success with rear fans blowing on the primary with vent holes above his 25" primary.

I was out with the CBLMS last night and in fairly steady seeing was getting sharp views of Jupiter at 373x and 474x intermittently. Unfortunately, the first iteration of this CBLMS probably cost about $2k to implement because we were doing first time engineering from scratch. I suspect that existing scopes could be modified using the techniques we incorporated for substantially less than this in subsequent iterations. For those that have not followed my thread on this forum, here is a picture of the front fan portion of the system. In the next post, I will show a picture of the rear sucking system of the CBLMS.

Edited by Bob S. (01/10/13 07:29 AM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | >> (show all)


Extra information
13 registered and 13 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 19896

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics