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Edge HD and Vented SCT Fan Systems

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#1 EFT

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Posted 30 November 2011 - 04:02 PM

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The TEMP-est TEMPerature Equilibration System for Telescopes vent and Fastar fan systems are now officially available for the C14, C11 and C8 Edge HD and new vented SCTs as well as the CPC Deluxe HD 8 and 11 models. They can be found here:

Edge HD

CPC Deluxe

Fastar only

All of the fan systems run off of 12VDC with very low amperage with the vent fans designed to run during viewing or imaging.

The only size we do not have yet is the C9.25 so I am looking for someone in the Phoenix, AZ area who can lend me their Edge HD 925 for a little while so that I can design the vent fans for it. The person that can help me with that will get a set of the fans for free once I am done. Please let me know offline if you have one in the area.

Thanks,
Ed Thomas
Deep Space Products

#2 skybsd

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Posted 30 November 2011 - 04:19 PM

Hello Ed,
I'm not sure I see how exactly these work, to be honest..,

From the product pages of the Fastar-only SCT models, the only addition I can determine is the component that goes onto the Fastar assembly on the front corrector. Is that it? Blow air in from the front?

Also, judging by the fact that this_is_the secondary_mirror here, I take it this is not a permanent, always-on solution and that one has to: -
- swap in your product
- run it for a while
- remove your product
- reinstall the faster assembly
- then, start using the scope

Is that the workflow?

Also, for the EdgeHD Series product, with and egress fan in one and an ingress fan in another, is the egress fan running at higher RPM that the ingress fan?

Have you worked out the airflow involved when in use? I'm mindful that this alone may well only result in air (in theory) being pulled across the back of the primary mirror - not that this is a bad thing, its just curious what quantifiable benefits can be expected..,

Do you have expected airflow diagrams and test data you can share at this time?

Thanks.

Regards,

skybsd

#3 EFT

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Posted 30 November 2011 - 06:37 PM

The Category 1 Fastar-Only models are for SCT that have the Fastar secondary but do not have rear vents like the Edge HD scopes or for people who only want to use the Fastar fan for fast cool down of an Edge HD or other rear-vented Fastar SCT. To use that model the rear of the scope has to be left open if there are no rear vents. The Fastar-only model is strictly for initial cool down of one of the Fastar-capable Celestron SCTs. In order to view or image with the scope the Fastar fan must be removed and the secondary replaced.

The Category 2 and 3 models are for the Edge HD, CPC Deluxe and new Celestron SCTs that have built in vents in the rear cell. In these models, the rear vents are replaced with active fan systems that push and pull air through the OTA and can be run all of the time. The vent fans are installed in the OTA and remain there. They can also be combined with the Fastar fan for initial cool down of the scope.

The vent fans are identical. However, the the egress fan flow can be increased by removing the filter from that fan for increased air flow. The total air flow depends on which scope is being used due to the different size fans required. The follow are what I currently use for the vent fans:
C8 - 0.7 CFM per fan
C11 - 3.0 CFM per fan
C14 - 1.2 CFM per fan
The Fastar fans have much higher CFM. Unfortunately, I was forced to go with a smaller fan in the vents for the C14 than the C11 due to the surprisingly small C14 vent size.

The idea of the vent fans is to not only help the primary mirror stay close to the ambient temperature but to help break up the air currents in the tube. There are two threads started in the Solar System Imaging and Processing forum that depict the results obtained using the vent fan system on a Edge HD C11.

Mars

Jupiter

I'm not sure what you are looking for in regards to airflow data and test diagrams. I can tell you that when I first started out on development I found that a single vent fan on the C11 could pull a vacuum in the OTA sufficient to draw air in the other side.

Ed.

#4 skybsd

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Posted 30 November 2011 - 07:59 PM

Hello Ed,
Thanks so much for taking the time to respond to my post here..,

The Category 1 Fastar-Only models are for SCT that have the Fastar secondary but do not have rear vents like the Edge HD scopes or for people who only want to use the Fastar fan for fast cool down of an Edge HD or other rear-vented Fastar SCT. To use that model the rear of the scope has to be left open if there are no rear vents. The Fastar-only model is strictly for initial cool down of one of the Fastar-capable Celestron SCTs. In order to view or image with the scope the Fastar fan must be removed and the secondary replaced.


Understood - thanks for confirming.., My reason for asking was to ascertain what the key differentiator is / are between this new product and existing ones for the same model scopes..,

The Category 2 and 3 models are for the Edge HD, CPC Deluxe and new Celestron SCTs that have built in vents in the rear cell. In these models, the rear vents are replaced with active fan systems that push and pull air through the OTA and can be run all of the time. The vent fans are installed in the OTA and remain there. They can also be combined with the Fastar fan for initial cool down of the scope.

The vent fans are identical. However, the the egress fan flow can be increased by removing the filter from that fan for increased air flow. The total air flow depends on which scope is being used due to the different size fans required. The follow are what I currently use for the vent fans:
C8 - 0.7 CFM per fan
C11 - 3.0 CFM per fan
C14 - 1.2 CFM per fan
The Fastar fans have much higher CFM. Unfortunately, I was forced to go with a smaller fan in the vents for the C14 than the C11 due to the surprisingly small C14 vent size.


Its good that there is a way to create higher egress airflow. The reason for my asking was to determine whether or not the products for EdgeHD Series models were designed to perform air exchange such that air is intended to be "pulled through" the environment via internal "natural" air pressures that results from minor increases in egress RPMs.

The idea of the vent fans is to not only help the primary mirror stay close to the ambient temperature but to help break up the air currents in the tube. There are two threads started in the Solar System Imaging and Processing forum that depict the results obtained using the vent fan system on a Edge HD C11.

Mars

Jupiter

I'm not sure what you are looking for in regards to airflow data and test diagrams. I can tell you that when I first started out on development I found that a single vent fan on the C11 could pull a vacuum in the OTA sufficient to draw air in the other side.


I appreciate the link references there.., I was keen to determine if the airflows resulting from your system has what has been identified as a key factor in SCT performance as the ability to manage the primary mirror boundary layer. I was literally excited to know whether or not you had managed to achieve active primary mirror boundary layer disruption - which has the potential to dramatically improve SCT views even though internal air temperatures have not yet equalized to ambient..,

Being able to show that using your products that the resulting airflow (as illustrated via a diagram) does indeed cause active disruption of the primary mirror boundary layer, and that you have managed to quantify / calculate image stability as a function of airflow rate across the primary mirror would be a huge step forward. Hence, my post..,

Please view my contribution here as that of enthusiastic hopes and my (almost) willing successful development for your product there..,

Thanks again, Ed.

Regards,

skysbd

#5 EFT

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Posted 30 November 2011 - 08:38 PM

I'm afraid that the math or computer modeling that could produce diagrams regarding the air flow through the system are probably well above my non-engineering background. Just determining air flow through a filter screen is not an easy task I have found. However, I think that with the obstructions to air flow in the back of the SCT and the total CFM moving through a fairly small volume, there should be sufficient movement of the air in the OTA overall to disrupt the boundry layer and currents in front of the primary. That was the intention of the design.

I am working on other possibilities for internal micro blowers that sit in front of the primarly but they will certainly be more difficult to install without removing the corrector which a lot of people will not want to do. I have also considered the possibility of installing vents in the tube in front of the primary, particularly in the C8 and C11 carbon fiber tubes that I carry. This might be something else I do but I am reluctant to get into too much drilling of holes in OTAs. That's the beauty of the new Celestron design with the vents. Once I have the current round of TEMP-est systems up and going I will be considering other systems that can be developed for other types of SCTs and OTAs and would be happy to hear from anyone that has an idea for something they need that others might find useful.

Ed.

#6 EFT

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Posted 30 November 2011 - 09:54 PM

One of my customers/testers is planning on collecting some quantitative data on the fan performance and effect once he gets some clear skies.

#7 skybsd

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Posted 30 November 2011 - 10:26 PM

That's good news, Ed!

Regards,

skybsd

#8 bilgebay

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Posted 01 April 2013 - 07:51 AM

One of my customers/testers is planning on collecting some quantitative data on the fan performance and effect once he gets some clear skies.


Hi Ed,

Did you have any progress on this ?

Cheers

Sedat

#9 EFT

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Posted 01 April 2013 - 08:31 AM

One of my customers/testers is planning on collecting some quantitative data on the fan performance and effect once he gets some clear skies.


Hi Ed,

Did you have any progress on this ?

Cheers

Sedat


Sedat,

Here are the write-ups: ATT Article and Wade Van Arsdale's website.

Ed.

#10 bilgebay

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Posted 02 April 2013 - 06:55 AM

Very impressive data Ed.

Do you know if some air can escape from or get into the tube from beneath the corrector plate on the C8 Edge?

This was the case with my C11 Edge but I remember reading on CN that C8 Edge corrector plate was kind of glued to the front cell.

#11 EFT

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Posted 02 April 2013 - 09:37 AM

The tubes are certainly not air tight, but for the most part, you can expect the air to flow through the easiest pathways (i.e., the vents) and much less through any other openings. Even the tube cells are not so tight as to prevent some air flow. Most, if not all of the EdgeHD correctors have some silicone glue of some sort in a few spots around the corrector although there appears to be no need for it.

#12 bilgebay

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Posted 03 April 2013 - 04:56 AM

Can I wire the the fans so that both work as egress fans ?

Thanks

#13 EFT

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Posted 03 April 2013 - 10:30 AM

Can I wire the the fans so that both work as egress fans ?

Thanks


The fans can't change directions by changing the wiring because they are mag lev fans, but they can be installed to blow either direction (i.e., just flip the fan over). If you were to use both for egress, then you would need a vent of some sort to let air in elsewhere. The Fastar hole would obviously work, but then you couldn't use the fans while using the scope.

#14 bilgebay

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Posted 04 April 2013 - 03:13 PM

Thanks for the info Ed.

Clear skies






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