GSO 8"rc secondary dew heater

[phatlad]

hi all i have had one or two nights where i have had my secondary dew up on my 8"RC, has anyone else had this problem? i was going to make myself a dew heater form resisters, but when i have taken out the secondary mirror cell it looks as tho the mirror is glued in.

is there anyone out there that has made a dew heater for this scope? or has striped one down and could help me please

thanks glen.

[Macavity]

Had it last time with 8"/F4 GSO Newt. Gave it a quick blast with hair drier.

Now looking at: Kendrick Split Newtonian Secondary Heater - Altair Astro

... Seems just the sort of thing for larger secondaries. I sense it's elliptical

for a Newt? People make their own from resistors... 12V/2W? <thinking>

[Rustysplit]

I use a dew band for a 1.25 eyepiece and wrap it around the mirror holder boss. Works a treat!! run the wires along the spiders as neat as you can though

[r3i]

I got dew so bad on some nights that the primary also started dewing up even with a dewshield. So now I've got a strap around the outside of the tube for the primary (one usually advertised for 8" SCTs) and a strap wrapped around the secondary that is 13" long and normally aimed at 3" tubes - I suppose it does slightly increase the size of the central obstruction but better that than a dewed up secondary.

[r3i]

Had it last time with 8"/F4 GSO Newt. Gave it a quick blast with hair drier.

Now looking at: Kendrick Split Newtonian Secondary Heater - Altair Astro

... Seems just the sort of thing for larger secondaries. I sense it's elliptical

for a Newt? People make their own from resistors... 12V/2W? <thinking>

Looks like Kendrick already do them for larger RC scopes: Kendrick Astro Instruments - Ritchey Chretien Heaters

Might drop them a line to suggest there is a market for similar ones to fit the GSO RCs

[r3i]

Looks like Kendrick already do them for larger RC scopes: Kendrick Astro Instruments - Ritchey Chretien Heaters

Might drop them a line to suggest there is a market for similar ones to fit the GSO RCs

Well I got a fast response from Kendrick and they are currently designing a heater for the GSO RCs that will be a similar design to the split ones they currently sell for the Newtonian secondaries.

[r3i]

The Kendrick dew heaters for the GSO RC secondaries are now available. Here's one installed in my AA8RC:

[philming]

Interesting. Doesn't the power cable ruin astrophotos ? Big stars must have strange spikes ?

[r3i]

Interesting. Doesn't the power cable ruin astrophotos ? Big stars must have strange spikes ?

Not that I've noticed - I've done my best to attach it along one of spider vanes, but then again I'm low down on the imaging learning curve and an odd shaped spike is the least of my worries. Also, since getting the heater, I've had little chance to try it out as we've been moving house this year - so looking forward to the autumn to get back in the saddle again.

[philming]

OK so I bought and installed the Kendrick dew heater on my RC.

I have glued it on the secondary mirror holder with silicone glue (the same as the one used in bathrooms i.e.)

Yesterday eve, the sky cleared so we went out.

The dew heater was powered on 12V via a Hiteckastro dew controler (2 dew heaters pluged in : the RC's and a ED80 standard strap):

http://www.teleskop-express.de/shop/product_info.php/info/p4669_Hitecastro-Mini-Controller-for-one-or-two-dew-heaters.html

I started shooting at around 6PM and finished around 12PM.

Temperatures went down to around -2°C

when I decided to stop shooting I realised the RC's secondary mirror was covered with frost. I checked, the dew heaters were pluged in, and set to the max power.

Is this normal in any way ?

Is there any way to get the dew heater to work as it should ?

Thanx for your input and best regards,

[The universal]

Howdy,

I have the rc 8" and the secondary dew heater

Am I right in thinking that the spider vane / secondary mirror should be removed before gluing the heater strip to the rear of the mirror housing. Or is the idea to go in guns blazing and glue it on while everything is in place on the actual scope.

It's hard to find much online about this dew heater. The instructions don't advise that you remove the spider vanes /mirror housing before attempting to glue it on

Can I ask how you attached the heater please

Thanks Andy

[astronymonkey]

I have a kendric eliptical secondary heater on my 16 inch dob and it works a treat.

it sounds as if you may have installed it incorrectly though as the heater needs to have a good direct contact with the back of the mirror.

If you attache it to the holder then the heat isnt able to conduct through the holder enough to warm the mirror. In my scope I completely romoved the holder and then took the mirror out of it to install the heater inside the holder meaning the mirror was in direct contact with it when it is fitted back in. This may move the secondary down the tube by a few mm meaning the holder may need to be repositioned slightly but once done it woks very well even in frosty conditions.

so this is my experience on a newtonian and im sure the same would apply to any set up in that decent contact is needed between the heater and the mirror to allow good heat conduction.

Cheers

[r3i]

Howdy,

I have the rc 8" and the secondary dew heater

Am I right in thinking that the spider vane / secondary mirror should be removed before gluing the heater strip to the rear of the mirror housing. Or is the idea to go in guns blazing and glue it on while everything is in place on the actual scope.

It's hard to find much online about this dew heater. The instructions don't advise that you remove the spider vanes /mirror housing before attempting to glue it on

Can I ask how you attached the heater please

Thanks Andy

Hi Andy,

You should not need to dismantle anything on the scope to fit the heater.  Just put some adhesive onto the heater strip, then attach it to the back of the secondary housing in such a way that the cables can then be taped around one of the spider vanes.

[astronymonkey]

Ive just had a good look at the kendrick website and despite my earlier email it looks as if you may have installed it correctly but either the heat isnt getting th the mirror or the heater isnt working. I note though that there may be different secondary designs so did you get the right heater for your type and make of scope.

cheers

[The universal]

Hi r3i,

Thanks, I just had visions of excess silicone dripping off onto the inside of the scope.

Thanks for your advice

[The universal]

Hello friends,

My kendrick heater came with red connections on both wires surround 2" from the heater.

In the official pics these connections aren't there

It's making it awkward to do a neat job of keeping a low profile when attaching to the spider vanes.

Are these connectors on your heaters? Why are they put close to the heater at such an awkward distance.

Also, when the heater is in place I have a gap of around1/2" where the two ends don't meet as I had expected.

This normal?

Only pics online are kendrick's pics (which dont have red connectors splitting each wire) and the pic from this thread

Thanks for your help

[Whitters]

My heater arrived in the same state, with connectors crimped to the wire two inches from the heater. I took the advice of using the adhesive copper strip as supplied. Glued the heater strip as advised, you only need a thin smear of the glue. Fit the copper strips I put one strip on each side of a vane. Cut the leads to length and solder the leads from the heater to the copper. Drill a couple of 2.5mm holes to take the leads which go to the power supply. Fit leads and solder.

[rpineau]

Nice work.

I have the AT12RC and the same heater doesn't fit between the vanes and the back of the secondary holder.. I wish it did (Already talked to kendrick about it and they have no option for now as it would require that they make a thinner one). I wonder if my secondary might be to far from the primary which would explain why the heater doesn't fit.

Anyway, your install look really good.. an example of how to do it for all of us.