Fan Club?

[drmorbius]

G'day all,

After that most excellent Cambroon viewing night on Saturday I've been seriously looking at scopes. I noticed that Andrews had a special deal on their 12" GSO scope, $100 cheaper without the fan.

Which prompted the question... do fans add that much value?

cheers

[davidpretorius]

yes to a fan, but not if the configuration is not sealed. check out matts sealed fan in the atm section. it helps cool the bigger mirror down and break the boundary layer much better than a fan simply blowing on the bottom if the mirror without sealing the bottom.

for $100 you should be able to buy a fan and then the materials to seal the end.

[iceman]

I don't think it's just the fan. The difference is the "premium" versus "standard" model.

The premium has the fan, as you say, but it also has the crayford focuser - which is a HUGE step up from the standard rack n pinion that you get with the standard model. It's worth it for that alone.

Having said that, you can buy the 10:1 crayford focuser which is even better again (in some cases - QA issues?) for around $120 and fit it yourself.

The fan is good though as well - it helps to cool the mirror to ambient temperature quicker than if you don't use a fan.

There's a bunch of threads about the crayford focusers in the Equipment forum - do a search and read what people have to say about it before making your decision.

[asimov]

Hi Randall. I reckon this thread by Matt pretty well answers your question.

http://www.iceinspace.com.au/forum/showthread.php?t=9600

A decent fan is worth far less than $100 so you *could* buy the scope & add your own later..

[matt]

Randall

$20 gets you the new computer fan, another $20 buys you the variable speed unit... both from D.Smith.

If you can do the cutting yourself or help from a friend, that's a nice little saving.

Even cheaper if you've got an old computer fan sitting around doing nothing and you don't want the variable speed unit. Just wire the fan to a battery.:thumbsup:

[iceman]

Stop confusing him peoples! :)

The $100 is for the crayford focuser AND the fan!

[matt]

But still... there's good savings to be had with a DIY primary mirror fan.;)

and, of course, the satisfaction of doing the job yourself...

[drmorbius]

Just to clear things up a bit... if you check the GS section of Andrews (http://www.andrewscom.com.au/site-content-section-10-guansheng.htm) you'll see the "SPECIAL Limited-Crayford version" of the GSO 12" Dobsonian, which appears to be everything in the Deluxe version (including Crayford focusser) except the fan... hence my post.

I was just curious how much impact a fan has on the viewing experience.

[asimov]

Yeah, pays to keep updated doesn't it? ;)

[matt]

So ... it does look like it's $100 for the fan...after all????:shrug:

[davidpretorius]

SPECIAL Limited-Crayford version features a 2" Crayford style focuser with a 2" to 1.25" adaptor, but NO fan.


well, first question, in queensland how much does your temp drop from dau to night??

does it drop significantly during the night

for me in tassie at the moment, it could be 17 degrees at 4pm and then 3 degress by 10pm. there is no way the primary mirror can cool in that time, so my viewing would be shocking

a fan will help

a fan with enclosed end like matts will be better

a peltiered cooled system is even better still

[janoskiss]

Mike, that's an old pricing scheme you're referring to. There are three versions now. Extra $100 for the Crayford, and another $100 for fan and right-angle correct image finder. Pity no more Rigel quickfinder it would seem. One of those (or telrad) is essential with a RA finder.

And yes, you need a fan. In a sealed baffle preferably.

[iceman]

My bad! Apologies for my confusion!

[asimov]

Don't worry Mikey! We won't hold it against ya! :)

[Gargoyle_Steve]

When I had my computer busines some years ago I used to buy the same fans for around $2.80 each (plus GST I think). If they're worth $100 each now I've got enough spare ones around here somewhere in a box to buy an entire new 12" scope!
:-)

[matt]

:lol: with Gargoyle ...

I think that's $100 for the entire fan set-up ... not just the fan.

But it's still a fairly hefty price, methinks...

[Gargoyle_Steve]

Matt I've got a 10" GS Dob deluxe version, I deliberated antied up the hundred bucks to get the Crayford with the fan as a bonus extra from my point of view. As far as I can tell the "entire fan set up" is a fan, about 7 inches of red/black figure 8 wire, and a small panel mount DC socket. If those bits costs more than $5 in parts I'd be very surprised, and that's what I could buy them at not GS's price. I'm not clear as to what else constitutes the "entire fan set up". Of course I didn't count the 4 screws that hold the fan in place ... about $25 each maybe? :eyepop:
All fun aside what I'm saying is it doesn't matter what the fan set up is they are not charging a hundred bucks for that alone, there's more to the story than that.

Randall if in doubt about exactly what version has what just ring them and ask directly what the differences are, that way you are not subject to any possible misprints or typo's etc. If you notice carefully the description of one version says it has the 2" Crayford focusor but it does not mention the 2" to 1.25" adaptor, yet it still comes with the same 4 eyepieces with 1.25" barrels.

By the way Randall my Andrew's 2" 30mm Ultra Wide eyepiece arrived today, gave it a real quick test before coming in to work this evening. Drop round one night and have a bit of a looksie through it, think you'll like it and you may want to order one at the same time you order the scope.

[matt]

I guess the price includes installation??? That's what I meant by "entire fan set up". Parts, labour etc

If you don't want the hassle of having to get the parts yourself and then cutting up backing plates and modding etc it has some value, I guess.

Although I'm all for DIY as my own cooling fan mod attests:thumbsup:

Some will see value for money, where others see a saving to be made with a mod at a later date.

Each to their own.

[iceman]

The price includes a right-angle finder as well, not just the fan.

See post above by Steve..

[matt]

Yeah. Saw that Mike:)

How's your fan/temp sensing mod coming along?

I had mine out last night but the wind here was more reminiscent of a bad Sydney-Hobart!!!!

I did, however, run the fan to see how well it helped the primary track ambient and I was happy with the result.

[iceman]

No progress yet.. the outdoor temp last night was 14.5° at 11:30pm - very mild!

I haven't had my mirror out yet to clean it and then attach the other sensor. Plan to do it on the weekend.. when I get home from work it's happy hour with the kids, feed, bath, bed etc, and then it's lie on the lounge time :)

[asimov]

I ended up buying the DSE 12V fridge & the temp. sensor unit too. No time as yet to do much like get the peltier system out of the fridge, but I did test the sensor unit out. Is seems reasonably accurate. I bunged one sensor in the fridge just to experiment a bit.

[matt]

Coooooool Asi!!!!

The "Chillin' Club" making steady progress;)

[drmorbius]

Thanks everyone,

After chatting with a few gurus, it sounds like a fan is not a bad thing to have. And if you didn't have one it could be easily added.

In fact, it sounds like... if you have a telescope without any personal modifications, you don't really have a scope! :D

So what's the doctor going to do now? Will his children go without food and shoes to fund the GSO 12" Dobsonian? Will his astro-widow have to get another job to fund his addiction? Stay tuned!

and thanks again! ;)

[Starkler]

No not at all. It's more like how some can satisfy their astronomy cravings when its cloudy ;)