First Light 10" f3.8 Astrograph

[mch62 (Mark)]

Hi back after a long absence , but finally have my new toy up and running ---sort off.
Just a quick post of the first photo from my home made Astrograph.
Features a 10" f3.8 Mark Suchting conical mirror FPI Protostar secondary spider and blacklite tube and a Clement focuser.
Photo is a single full frame unprocessed resized and converted to jpeg only 90sec shot from an unmodified Canon 50D DSLR camera and MPCC and no guiding on an EQ6PRO.
It was taken under a full moon and focus was off a bit but wanted to see how the MPCC works at F3.8.
I hope to get an ASA Keller .73x reducer corrector soon and EQmod working properly.
Mark Suchting is doing an F3.5 and F3.2 ,it will be interesting to see how they go.

Regards Mark

[[1ponders] (Paul)]

Looks promising Mark.

It was great to catch up at astrofest. You'll need to pop out here one weekend when you visit the family at Eumundi. I'm only half an hour away...and very dark

[mch62 (Mark)]

That a given Paul , will be out there as soon as I get EQmod sorted.
I hope to have a star party my way possibly next week end ,just checking a few things first.
Astrofest was great as usual and got some good info from it.
Mark

[[1ponders] (Paul)]

could be a challenge next week. Ron's is on this weekend and the following weekend is Barambah

[DavidU (Dave)]

What a nice job. 90 sec !
Get that guiding under control, a stack of 90 sec subs, processed it will come up superbly.

[Satchmo]

Mark, Just a suggestion, If you lop off the excess length of tube past your mirror cell you should increase the resonant frequency and decrease wind profile a little.

[mch62 (Mark)]

Thanks for the suggestion , I am planning on doing that but am waiting untill I get the Keller corrector just incase I need to slide the mirror back a bit.The wind is not much of a problem in the observatory except the bit that sticks out the top.But yes any reduction in length would be a small help in torque on the dec motor ,weight not so much these blacklite tubes arn't that heavy.
Mark

[lacad01 (Adam)]

Well done on the project Mark
Now for a completely dumb question but the term astrograph - does that refer pretty much to a purpose built newt or reflecting telescope primarily for astrophotography i.e. you wouldn't use it for visual observing necessarily ?
cheers

[mch62 (Mark)]

I think the term loosly refers to a scope weather it be Newtonian or any thing else has been optimized for Astrophotography in that the fully illuminated field created by a larger secondary will fully illuminate the larger imaging plain required.They also tend to be a shorter F number for faster imaging.This results in a larger than normal secondary ,not a concern for deep sky imaging but not desirable for planetary imaging.
Some times it is hard to get eyepieces to come to focus in an Astrograph as the imaging plain has been designed for a camera.
I have used a Clement focuser which has 3 inches of travel and does not protrude into the light path and has a low 1 inch profile and as such can just get my DSLR to focus with it racked all the way and to the other extream my TV 12mm Nagler I think , almost all the way out without using extensions or spacers.
With my old 12.5" Newtonian f6 it was optimised for planetary imaging with a smaleer secondary 17% If I can remember and as a result even with an optimised tube focuser design only had a 12mm fully illuminated field which is more than enough for smaller planetary cams and visual observing but not enough for a larger chip.
Astrographs quite often have other optical elements to correct for aberations and flat fielding ect ect.
Any way I have only dropped an eyepiece in the new scope twice ,it always has the camera attached.

Got some more RAW images from last night & have not had time to process them but just getting the feel for the scope and imaging times and seeing how the guiding is working. Still got some bugs there but here is another RAW converted to Jpeg and resised only.4 mins ISO800 D50

Mark

[Ian Robinson]

Nice rig....

I'm not far off finishing my 10" f4.66 (which will be used visually and to image via my Lumicon coma corrector and esyguider) and will be put ontop of my New Atlux (looking forward to trying it out at last , I've had it for over 12 months and not taken it out of the house yet ....).

I too looked at buying one of those 2" 0,76x ASA correctors
http://www.astrosysteme.at/eng/correctors.html
but they are PRICEY .... I'll make do with the Lumicon coma corrector and my Baader MFCC for imaging and my Paracorr Visual for when I'm just looking.

Once my OTA is complete (maybe in a day or two) , and I've boned up on driving the Starbook controller , I'll have some fun trying it all out this dark ..... bet the drought breaks and all I see is clouds !!!

Then it's onto getting serious about the ROR shed (umm.... observatory) .... might be all set up by Xmas maybe.


If the long range weather forecast for Qld and NSW is wrong and it clouds up and gets very wet over the next few months .... blame me if it's not because of Mark's new kit.

Mark , how big is your secondary ?
I take you have a 2" low profile crayford focusor too , or did you opt for a 3" low profile crayford (assuming they are available) ??
Did you flock the inside of your tube ?
I just completed flocking mine last week and have been static testing the adhesion of the flock to make sure it stays put before installing my optics.

[lacad01 (Adam)]

Thanks for that explanation Mark

[mch62 (Mark)]

Ian I went the 2 " focuser as I had a 2" Clement focuser from my old scope.It gives a 1 " low profile no obstruction into the tube but a 3" travel.Downside big and bulky and a tad heavy but it does not slip.The diagonal is 79mm which gives about a 24mm fully illuminated field.It's a bit under a DSLR chip diagonal but at the time funs didn't permit buying a 3" focuser to allow for more unvignetted light.I was toying up with getting a 3" Clement focuser.There is also one available from Jims Mobile JMI.
Yep the ASA reducer is very expensive almost as much as the Mirror but is made with an ED element. I have been hoping to upgrade my mount as well but thats an even bigger leap of $$$ as I have a 14.5" f3.5 on my mind.
My tube is called a Blacklite tube from where I got the diagonal FPI Protostar.It's preflocked saved a bit of messing around.
http://www.fpi-protostar.com/blite.htm
She's dark inside there.I experimeted with a green laser pointer at different angles on different materials looking for a flock material and this stuff they use on the inside shows no reflections or light scatter.
So far I am getting very good results from the MPCC at F3.8 which does make it hard to justify the ASA corrector reducer.
Mark

Originally Posted by Ian Robinson

Nice rig....

I'm not far off finishing my 10" f4.66 (which will be used visually and to image via my Lumicon coma corrector and esyguider) and will be put ontop of my New Atlux (looking forward to trying it out at last , I've had it for over 12 months and not taken it out of the house yet ....).

I too looked at buying one of those 2" 0,76x ASA correctors
http://www.astrosysteme.at/eng/correctors.html
but they are PRICEY .... I'll make do with the Lumicon coma corrector and my Baader MFCC for imaging and my Paracorr Visual for when I'm just looking.

Once my OTA is complete (maybe in a day or two) , and I've boned up on driving the Starbook controller , I'll have some fun trying it all out this dark ..... bet the drought breaks and all I see is clouds !!!

Then it's onto getting serious about the ROR shed (umm.... observatory) .... might be all set up by Xmas maybe.


If the long range weather forecast for Qld and NSW is wrong and it clouds up and gets very wet over the next few months .... blame me if it's not because of Mark's new kit.

Mark , how big is your secondary ?
I take you have a 2" low profile crayford focusor too , or did you opt for a 3" low profile crayford (assuming they are available) ??
Did you flock the inside of your tube ?
I just completed flocking mine last week and have been static testing the adhesion of the flock to make sure it stays put before installing my optics.

[netwolf]

Mark, congrats glad to see this project is finally of the ground. Cant wait to see what you produce with the Keller corrector/reducer in there. This should put up some nice competition to the ASA Astrographs.

[mch62 (Mark)]

Fahim did you get the Bartel controller hooked up on your g11? I am looking for a larger mount and possible a Titan size but not wrapped in the Gemini?
Wish there was something in price between the g11 and Titan.In the States the Celestron mounts look well priced but not here?
Mark

[netwolf]

Mark yes i did get it hooked up and going, but have not had any time to use it yet. Busy with new baby and moving house. Maybe consider getting a used AP QMD (non goto version). One of the guys on the Sitech yahoo group has converted one of these to the Sitech Goto system.

[Ian Robinson]

Originally Posted by mch62

Ian I went the 2 " focuser as I had a 2" Clement focuser from my old scope.It gives a 1 " low profile no obstruction into the tube but a 3" travel.Downside big and bulky and a tad heavy but it does not slip.The diagonal is 79mm which gives about a 24mm fully illuminated field.It's a bit under a DSLR chip diagonal but at the time funs didn't permit buying a 3" focuser to allow for more unvignetted light.I was toying up with getting a 3" Clement focuser.There is also one available from Jims Mobile JMI.
Yep the ASA reducer is very expensive almost as much as the Mirror but is made with an ED element. I have been hoping to upgrade my mount as well but thats an even bigger leap of $$$ as I have a 14.5" f3.5 on my mind.
My tube is called a Blacklite tube from where I got the diagonal FPI Protostar.It's preflocked saved a bit of messing around.
http://www.fpi-protostar.com/blite.htm
She's dark inside there.I experimeted with a green laser pointer at different angles on different materials looking for a flock material and this stuff they use on the inside shows no reflections or light scatter.
So far I am getting very good results from the MPCC at F3.8 which does make it hard to justify the ASA corrector reducer.
Mark

14.5" -15" f3.5 on my mind too .... I think my Atlux will handle it for imaging no sweat (expecially if I do a ultralight tube (carbon fibre) ie something like http://www.orionoptics.co.uk/AG/agrange.html# (a 14" f3.8 comes in at 20kg , and their 16" f3.8 comes in at 23kg .... carbon fibre tubes .... !!! great stuff) or maybe a truss tube.... that's probably several years off in the future for me. (I;d rather build it myself (buying the optics and hardware .... will save a stack on shipping that way .... wonder if Orion Optical sell the builtin Wynne Correctors separately ?

My crayford is 2" , has 2.53" of uptravel and extends about 50mm (I can adjust that a bit by several mm as well as rotating the focusor) above my tube when fully racked-in. My drawtube is 4' long. I considered a 3" low profile crayford , but decided I didn't need it. Maybe I'll go to 3" crayford when I build the bigger scope . I may have bigger chip camera by then .
I also want to be able to look through my scopes (most the time).

I've a 2.6" diagonal and I get 89% illumination out at 33mm diameter at the focal "plane" , more than good enough for my 40D even if there is a Lumicon Coma Corrector attached to the EsyGuider between it and the secondary.
I might one day upgrade to a 3" diagonal if I find I think I need better illumination over a wider field.

Yet to test the now assembled 10" astrograph reaches focus in EsyGuider mode , got some issues re collimation to come to grips with first. I've been fastiduous with my calcs and spacings and got it all as close I could to the spacings recommended by Fry's online Newt Design Program.