IC434 first light with 16" RC

[dtandy]

Finally, after six months of effort, the 16" RC I designed and built had first light this weekend. I shot a quick LRGB image of IC 434. Exposure times are 25 minutes in L and 15 each of RGB. Transparency was average for this time of year (ok but not great). I didn't bother to exclude the images with satellite trails since I was too excited to see how everything turned out.

The imaging system consists of a Paramount ME carrying a 16" F6.5 Ritchey Chretien with Star Instruments optics and a FLI PDF focuser, Tak FSQ106ED, Celestron 80mm F11 guidescope and a SBIG STL-11000M with Astrodon filters. I shot the image and did some initial processing while Jon Walton teased a bit more detail out of the image using Photoshop.

Regards,

Dave Tandy

[budguinn]

Dave,

This definetly looks like it is going to be a winner.....from the image displayed it looks like you have very nice round stars from corner to corner...and very nice detail.

bud

[BT Technologies]

WOW Dave!! Very nice "first light" for your new RC!! I see you also caught a sattellite in the lower right and upper hand portions of your image!

Beautiful...

Originally Posted by dtandy

Finally, after six months of effort, the 16" RC I designed and built had first light this weekend. I shot a quick LRGB image of IC 434. Exposure times are 25 minutes in L and 15 each of RGB. Transparency was average for this time of year (ok but not great). I didn't bother to exclude the images with satellite trails since I was too excited to see how everything turned out.

The imaging system consists of a Paramount ME carrying a 16" F6.5 Ritchey Chretien with Star Instruments optics and a FLI PDF focuser, Tak FSQ106ED, Celestron 80mm F11 guidescope and a SBIG STL-11000M with Astrodon filters. I shot the image and did some initial processing while Jon Walton teased a bit more detail out of the image using Photoshop.

Regards,

Dave Tandy

[dtandy]

Thanks. It was a relief to finally get everything working after a number of glitches along the way. Of course, now that the scope is built, I have about a dozen design tweaks I'd like to make!

Dave

[JMS]

I am very curious about how you built it. Did you build it from scratch and have the mirrors made? I have been contemplating this myself. I have a small machine shop and I am always making astro accesories. I am currently trying to make an 8 position filter wheel. www.jmsastro.webs.com

Joe

[Edsport]

Very nice Dave. Good luck with your new scope...

[dtandy]

Joe,

I had Star Instruments make the optics for me and I had a machine shop make all of the metal parts. I made the carbon fiber tube in my garage.

I have access to a nice CAD program at work so I used it to design everything. I did some basic FEA analysis to give me confidence that my design would be rigid enough and, based on my TPoint model results, it looks like I was successful. At 2635mm focal length, a 200 pt TPoint model puts any object dead-center on the chip every time. With the basic six terms the pointing RMS is about 150". With only two additional terms, the pointing RMS dropped to 32" with sigma's on all of the model terms less than 12 and in all but two terms more like low single digits. It appears that flexure is low and predictable. I've been able to go 15 minutes unguided but I typically autoguide as going unguided for 15 minutes is not always a sure thing.

I was seeing what I think were some thermal effects in my system but I am not totally sure. The rotational orientation of the secondary to primary is very important in order to obtain round star images. I was chasing my tail for a few nights trying to find the optimal orientation. Although the optics are marked and I was careful to install them close to their proper orientation, I still had to use actual images to help me dial everything in. I may need to have the shop lick off a few thou's on my secondary mirror holder as there is the possibility that when it gets cold (<32 F) it may be putting a bit of pressure on the secondary causing some slight distortion. I'm not sure, though, and now that the nights are getting warmer I am leaving well-enough alone.

The only advice I will give is to make sure you are willing to tolerate the possibility of making some mistakes that may be costly. Unless you are a very experienced telescope designer, you'll essentially be building a $12k prototype that may not work as well as you hope. The optics are expensive and machining isn't cheap. I was getting pretty nervous that I had some serious flexure when I was struggling to get round stars. Now that I seem to have the problem fixed, I still have several design tweaks I'd make to the scope just to refine a few things. Fortunately, none of them are performance oriented, they are more oriented towards ease of assembly/disassembly.

Overall, though, I think that the scope is going to be a very solid performer and I'm pleased that my design apparently is nice an rigid.

Dave

[stargazer]

congrats on your techincal skills! it looks A.O.K. !!!

[neilfleming]

Sweet setup! I have no mechanical skills...just a credit card <g>.

Nice shot, too!

Well done...Neil

[JMS]

Well, that $12G prototype just scared me away. Maybe when I retire and I am well off , but for now I have kids to raise. Good luck with it, and look forward to your images with it.

Joe