Outrageous

[Bassnut]

Its getting silly :P

I just picked up a S/H 10" RCOS RC from Peter Ward, on removing the dust cap, the original bubble wrap was still on the secondary focuser, this mother has never been installed, yet alone used :D .

mmm, RCOS, ME, SBIG, where the hell do you go from here?, am I in heaven??.

Carbon fibre tube, built in dew heater and focuser, ceramic mirror, the end of focus drift.

I think Ill get pissed now :whistle:

[Doug]

You could pawn your SBIG and go Finger Lakes instead.

[Bassnut]

Well, you have a point there, a thinned back illuminated CCD would be the go, but at US$30K a pop, it would be hard to get round the wife :P .OK, perhaps true nirvana is a few megabucks away, but thisl do me hehe.

Im fanancially "stressed" as it is, maybe next year :whistle: .

I see some pretty good results round here with a DSLR/ED80, the pressure is on, no crap postable now.

[iceman]

Beautiful looking gear, Fred! You must be pleased.

When does it get its first drive on your shiny new mount?

[g__day]

Wow Fred and I thought the RCOS looked great and I wondered if a G11 would do it justice, until I saw you've really gone all out getting the Paramount.

Your shots on the previous rig look great by the way, love to take you up on that offer and see your new rig in action later this year. I can only wonder what you'll be able to do with that!

I'm curious, given our light pollution can you do shots much longer than 10 minutes without getting too much ambient sky glow (I'm alot closer to ELS park than you and their mega-watt arc lights are only there to annoy me)! Do you get long duration shots by stacking or using filters or is it that your ST8XME simply leaves my poor little Canon 400D in the dust or all of the above and more?

What tips might you give an enquiring astrophotographer in his first year who has spend maybe 1-10th the time and under 1/5th the equipment budget you have devote to the night skies?

Matthew

[Bassnut]

Mike, Ill get it up within a week, but I want set up to be smick, so no rush.

Matt, well, expensive gear doesnt an expert make ;-) , ive got some catching up to do to get the max out of it.

I must confess, this set up is rather more than I would allow myself for personal use in the backyard. Its to be installed in a country dark site where I hope to sell remote imaging time on it.

No, I rarely go longer than 10mins (the ST8 has hi QE). Light pollution and tracking also becomes difficult longer than that (well, not with an ME ;-). Signal always grows faster than skyglow background, no matter how long the exposures, but its deminishing returns. Internal noise becomes a big problem past 10mins on a DSLR anyway. Stacking then becomes the way to improve signal, the more the better. So, no, generally a cooled CCD doesnt leave a DSLR "in the dust" (for brighter objects anyway), there are lots of amazing DSLR pics around where its hard to tell if it was taken with a CCD or DSLR.

Narrowband filters is where it gets to be fun, skyglow has far less effect, but youd really need to mod a DSLR to use them.

Some would disagree, but for pics taken with average gear, set up the best it can be, in polluted skies, the biggest image improvements comes from skills in and time with Photoshop CS2.

Cheers

[jase]

Great work Fred. No truss? Ion-milled optics?

So what will be the imaging train configuration? Native is 2286mm F/9 - .82 arcsec/pixel with the ST8 (FOV 14x21 arcmin). You don’t want to change it too far from its native configuration i.e the spacing between the primary and secondary when you’re installing a focal reducer (assuming you will). I guess you can always 2x2 bin to give 1.65 arcsec/pixel which is perhaps more realistic.

http://www.rc-astro.com/resources/reducer.html
http://www.hiddenloft.com/notes/rc.htm

[Bassnut]

Cant get picky with S/H RCs in OZ Jase, they dont come up very often. I couldnt resist, it could take a year for a new one (well, 1-2mth for an ion milled model, but thats another US$6k just for that). Its reliability and thermal stability Im after, RCOS is hard to beat.

Ill use the AP 0.67 reducer I have, this will give a sweet 1.23 arcs/pix at f6, or, apparently I could space it out to f5, wider will hopefully mean I can use internal guiding without a rotator. The dichromatic splitter youve mentioned before is might attractive but pricey, I might fit an OAG to avoid guiding through filters. Id really like to use external guiding, but I have been told repeatedly differential flexure is unsolvable for exposures longer than 10min, I still dont believe it, Im going to try locking down hard (no rings etc) the guide scope, focuser and cam and see what happens.

BTW, why do you say changing the primary/secondary spacing be such a problem?, the ST8 is small format, no vignetting. I was hopeing to possibly do just that to go to f5?.

Cheers

[jase]

Sorry, I missed the S/H bit. I thought you were talking about A$18k worth of kit. S/H would have been a bit cheaper, but alas limited options such as astrosital glass etc. Still kick butt none the less.:D

I prefer on-axis than off-axis, but there are merits in both methods. I use on-axis, even with the narrow band Ha filter (which is typically darker than SII and OIII filters). Simply bin the guide chip and increase exposure times between 5-10 sec. Works a treat. Helps to have an accurate tracking mount (PEC enabled) and good polar alignment. I don’t have problems in taking 30min subs on-axis guided with the Titan. If the Titan can do it, the ME will do it easily. Finding guide stars isn’t an issue with an instrument rotator. However, for robotic setups such as yours you need to consider usability – don’t want the system to be difficult/complex to use hence the beam splitter would make it attractive. The acp3 interface does simplify things.

I don’t think I can explain the native configuration better than Russ. It has nothing to do with camera type or size, but how the optician has figured the hyperbolic mirror sets and the optimal distance between the primary and secondary mirrors of the RC.

“A consequence of the Richey-Chrétien design is that the spacing between the primary and secondary mirror must be kept very near the value intended by the optician who figured the mirrors. If this spacing is allowed to deviate much more than a few millimeters, significant deterioration of performance will result due to spherical aberration.

The method of focusing by moving the secondary mirror is thus at odds with maintaining the performance of the system. The solution is to locate the instrument, be it a CCD camera, an eyepiece or what have you, close to the focal point of the telescope with the secondary mirror at its proper distance from the primary. The secondary focuser can then be moved only for fine adjustment of the focus.

Adding a focal reducer into the mix complicates matters. With the reducer in place, where is the new focal point of the system? How does one determine the correct position of the reducer such that the system will be nearly in focus without having to move the secondary mirror from its optimum position?” – Reference - http://www.rc-astro.com/resources/reducer.html

I suggest you read the above link.:thumbsup: Feel certain Brad will know about the spacing requirements etc.

[Doomsayer]

Nice to see some good kit! I just got my paramount ME in from New Mexico last week. My observatory in Newcastle is still under construction, so I'm a little behind you. I think my PME had a 20" RCOS on it up in the US - for the moment, I will battle away with a 12" SCT/ST8 while my L-plates are on. I must say, the ME is truly a work of art, in the engineering sense.

I'll be interested to hear/watch how you go.

cheers
guy

[Bassnut]

Jase, very interestink, youve bought up some interesting stuff, heavy link, but must be read, homework todo. Interestingly, the RC came with a bunch of different length spacers.

Guy, welcome aboard, yes, just looking at it is fun. Its robotic behavior is interesting, remember to set it up for the sthn hemisphere, apparently missing that is a common problem.

You will have fun with a 12" SCT on it, it throws it round like it wasnt there, and the guiding is a wonder, flat line error graph. Stars are not only round, but smaller without the typical wander on other mounts.

Cheers