Imaging with a Dob

[skywatcher250]

So I have the skywatchers truss tube version of 250px, according to several sources you apparently can add a 'wedge' and this in turn can mean you don't need an EQ mount.

Is that right or have I misunderstood this. If such a thing does work does it work well ?

[brantuk]

I think this is what you're thinking of - plenty of info on this site:

http://www.equatorialplatforms.com/dobsonians.on.platforms.shtml

[skywatcher250]

Just to point out I have the goto version but as its alt az rather than eq it obviously can't track. I can see these are a huge amount of money ( I may as well buy a second AP eq scope for that haha) I guess I mistook when I read the term wedge I thought something could be added to alter the alt az to eq somehow

I realise that's a big task, but wondered if it could be done. On a side note despite reading that the dob tube can be added to a heq5 I hear it can come with a lot of problems and therefore isn't recommended?

thankyou...

[jabberwocky]

RikM uses his 250px OTA on his NEQ6 for imaging, but he has the solid tube version. Not sure if you have enough tube to attach tube rings to get balance for imaging.

Best bet would be a separate imaging scope.

[skywatcher250]

hey jabberwocky - funnily enough i was just looking at his pics !!!!!

yeh im actually starting to think about that - im contemplating getting rid of the 250px (i used to have a 200p on eq mount) kinda wish i still had it.... hmmmm very much in 2 minds - trouble is im not using the 250 much - i kind of prefer getting my camera out now ! almost tempted to go for a small very portable imagine rig.... does such a thing exist ?

[DaveS]

I suppose the smallest, most portable rig would be a DSLR with lens on an Astrotrack, but they aren't cheap.

Beyond this there's the standard recommendation of an 80mm ED refractor on an HEQ5. It's the standard recommendation for a reason. It just works.

Oh yes, and get hold of "Making Every Photon Count" by Steve Richards, our own Steppenwolf

[skywatcher250]

Haha that's the very book that's making me sell my dob and look into this

i will check that refractor out now. Thanks

[skywatcher250]

http://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-pro-heq5-pro.html

I assume this ?

[DaveS]

Pretty much, yes.

Also budget for a focal reducer / flattener and a T-Ring to connect to your 7D. If you suffer from light-pollution to any extent then a LP filter is pretty much an essential.

Check out the kit in my sig.

[knobby]

Watcha Si, I think if you are going the AP route then the Dob needs to go !

It's not going to be cheap this AP lark :-)

Do you have a liver or kidney you could sell maybe ?

[skywatcher250]

Haha no. The comments on this and also the laser collimator post I made in the other forum have all got me a bit confused. I need to decide on my route. I am 90% sure I want to sell the dob now and start thinking about a more portable refractor. New ball game

[knobby]

I guess one of these is your starting point then.

http://www.firstlightoptics.com/skywatcher-mounts/skywatcher-heq5-syntrek.html

http://www.astrobuysell.com/uk/propview.php?view=69127

Then add a Refractor later ...

you can use the 7d on the mount while you decide wether to sell the liver or the kidney

[skywatcher250]

im now not 90%, haha - much less sure now

[valefor]

Just to point out I have the goto version but as its alt az rather than eq it obviously can't track.

i thought all goto's tracked. did i missunderstand this? im interested as im thinking of ditching my 8" newt in favor of a sw 300p goto flexitube.

here is a quote from green witch in there sw dob section. have i missunderstood?

"Skywatcher have now introduced a GOTO version of their populat Flex-Tube Dobsonian Telescopes. 'GOTO' means it will find things and track them for you automatically."

[skywatcher250]

Hey there my apologies it was a matter of speak. What I meant was the alt az will not follow the RA axis such as an equatorial mount will. Therefore not 'tracking' in my description should have said something along the lines of 'wont follow eq to allow imaging. Btw the goto 'goes to and holds' very well indeed on these. I can leave anything in the EP for hours disappear and make food etc and come back 3 hours later and it's still exactly central.

[skywatcher250]

And valefor. Just to clarify further it will do what it says but u have to set it up each time. Very easy once you know how but like anything can take a few tries

[Matt Scunthorpe]

You have to set any goto or tracking mount up everytime unless you can have it mounted on a peir or similar.

I use a HEQ5 pro and 200p currently for imaging with my DSLR. Will get an ED80 when im not skint lol.

[valefor]

ah thats ok then. so you can use a dob with a goto for imaging?

[skywatcher250]

not really - maybe with a webcam on the local stuff - ie moon / planets

the problem with a dob is not the tracking its the mount (specifically the axis it follows)

it uses an Alt Az mount as oppose to Equatorial (ie it doesnt follow the earth rotation precisely so images wont come out right at all)

that said some people manage it - you can look on google maybe at EQ vs ALT AZ mounts for more info - if you want to image stick with an eq

as i say saturn / jupiter will work with a webcam on a dob

[valefor]

aww that sucks. i was so tempted by the dobs relative cheepness and huge appeture. maybe il just save for an eq6 pro synscan and use my 8" newt with it.

[valefor]

just checked. for a mear £200 more than the equivelent sized dob i can get a 300p newt on an neq6 pro goto mount. that cant be bad for imaging.

[Matt Scunthorpe]

Apperture is irrelevant for imaging. Your best bet would be to get an ED80 (80mm apperture) and stick in it on a HEQ5 or NEQ6.

[DaveS]

Good as the NEQ6 is, I'm not sure it would be up to the job of imaging with a 300mm Newt. Assuming it's the Skywatcher 300, it's f/5 so 1500mm fl.

For imaging, it's FL (Image scale) and FR (Photographic speed) that are important. Aperture only come from the math.

[skywatcher250]

i guess what it comes down to is who you are and what you want... for me im am literally at biting point and could swing towards imaging or not....i am in love with my canon 7d and its a cracking thing ! the question is... do i want to hook it up to a scope, polar align it, and go through all the other motions and then hope its not raining, or the seeing isnt bad etc etc VS just simply looking through my lovely Hyperion EP and just viewing deeper with bigger aperture - im literally on the fence... but for now i own a big DOB and i think ill stick with it

theres so much that can go wrong with imaging and totally ruin your shots, however its very rewarding when you break the back of it... for now i think im going to mod a web cam and enjoy our stellar bodies

[Matt Scunthorpe]

I think Skywatcher has got it spot on

Since i put a DSLR on the scope, ive not done much visual, but i do enjoy both, so i do what ill enjoy at that moment Nothing wrong with having the option to do both. Although may mean more cost in the short term, but it very worth it in the long run.