Will PMX + C14 fit into my Sirius 2.3m dome?

[DavidNg]

Hi,

I am thinking of wading into planetary imaging and tempting to purchase a C14 OTA to be mounted on existing PMX in the Sirius 2.3 dome, using DMK camera. I've never seen a C14 in real life, in the pictures it looks humongous. Will the setup fit OK into the dome?

Thanks in advance.

Regards
David

[el_draco]

It will be tight. The C14 tube is about 1m with cameras, no dew shield. Hope you have extra Cw's. The PMX is also a big mount. Graham http://www.iceinspace.com.au/forum/member.php?u=5952 has an MX in a smaller dome and can probably give some indication. I'm building a 3m 5/8 dome to house a PME II with a C14. That will still be pretty tight but its a complicated system.

[Bassnut]

Oh dear, you need to think long and hard about that, your heading for a hiding, do homework. Not my experience BTW. Someone I know fitted a large long FL tube in a small dome and it was a disaster, endend up trashing the dome and moving to a roll off. Thermals in this situation worsened seeing by 2 arcsecs, it was awefull, although they did have large day/night temp transitions. If you increase FL for planetary to say 6m and more (seems thats what planetary guys do), its going to be much worse, thermal management is going to be a serious problem.

[graham.hobart]

Cheers El Draco
I have a PMX in a Sky Shed POD which is 80 inches (203cm) at the dome rim.
This is measured at the level at which the scope slews so is the working level.
I can tell you that an RC 10 tube is about 62cm then you add the extension rings , focuser and camera. With my QSI I was struggling to slew, with the SBIG and the filter wheel and the AO8 I had to put everything far forward and balance really carefully, even so I had to remove some parts to cross the meridian so is not comfortable for an automated set up at all.
I actually thought about making a NW to NE "gate which is removable so I can slew with more abandon, but it would structurally alter the walls.
I would guess in a 2m30cm dome, even if you place exactly central, with a metre long OTA plus cameras etc you would be squeezing it.
You could, if needed, I suppose, store the scope in a tight against the dome position and when ready to go, whack it straight into the dome slot-plenty of room there with the snout in the air!!
Graz:question:

[DavidNg]

Currently my refractor is slightly over 1 m long plus larger CCD, filter wheels,flatterner. The C14 has 787mm tube long, thus I think the length will fit ok into the dome, the width is another concern 14" obviously will take much more room than my 6" refractor. Guiding will be an issue too, piggyback mostly like will be out of question as the dome slit wont accommodate both. I do have 2 extra counter weights.



Thank you Fred, it is true the dome has thermal issue, in the summer the temperatures hover mid 30C most days sometimes more. I always open the door with fan running for several hours before imaging, yet autofocusing was still an issue, the first one or two images often poorly focused. In winter season the thermal issue is not as bad. That was with 6" refractor, it seems the C14 will be worse. I will find some ways to manage this. Thanks for your advice.



Thanks Graz, my pier is very much in the center. Currently my AP155 + Flatterner+ FLI Proline fit well enough, I am automating the rig without any problem so far. The C14 is I found out actually shorter by 20cm or so, but much bulkier, piggyback wont be any good though. Not sure if guiding is required for planetary imaging. I am new.

[Shiraz]

guiding is not required for planetary, but thermal management is critical.

[jase]

Yes, a C14 will fit into a 2.3 Sirius dome. Doug George (MaximDL developer) had a similar configuration on a Paramount ME a long time ago. Doug's old set up can be seen here - http://cyanogen.com/doug/construction.html
You would be surprised what you can fit. I had my 12.5" RCOS in mine for a while which I found a little scary. Peter Ward has fitted a 14.5" RCOS in his 2.3 Sirius dome before. Neither of these are small scopes.

If you are automating the shutters, just make sure the scope is parked and/or dome rotated into a safe position before shutter is closed. The lower shutter actuator enters the dome a fair way when closed. You could easily smash it through your corrector plate if not careful. When the shutter is open, its not a problem. Of course, if you are not automating the shutters, no need to worry about it as there is no actuator for manual operation.

[DavidNg]

Any tips for thermal management? so far I just open the dome shutters and door for several hours and run a big stand fan to facilitate circulation.




Thank you Jase, it is reassuring to know the Sirius 2.3 can accommodate 12.5 and indeed 14.5" RCOS fully geared. I am using automated rotator and shutters, will definitely look for the actuators when closing the lower shutter, something I never thought of. I will keep everyone updated. Cheers.

[AstroJunk]

Here's mine.

I would say that 'Cosy' would be the best way to describe the fit. As I use the scope remotely the issue of being thumped by a counter weight goes away, but don't expect the observatory to be a comfortable place for you and the scope.

Thermal issues - None, but I don't put a 1Kw heater inside when I use it - ie me!