Astrophotography help

[lesbehrens]

hi. well i am interested in starting in this field but no success yet.
i have tried modding my 10"dob to suit this field but result are close but not close enough.
is there a telescope where u don't need to mod the scope for a slr?
will a ccd cam be better for the 10" newtoian ?
please help....:help:
les

[Jeff]

Hi les, with most dobs you need to either buy a lower profile crayford focuser(which might get you an extra 10mm or so), or more likely shift the mirror cell up up the dob tube (not as hard as it sounds .... with a cordless drill and a pop rivet gun).

Have you read iceman's article on photography with a dob?

Jeff

[lesbehrens]

hi. yes i have tried both options . i put a low profile focuser in but that didn't work so i then got longer bolts to move the mirror up. but each time i try something different i am always short of focus. i then thought i could still use it for visual but found out u can't Whit the mirror up and with the focuser.
i want to do both visual and photography but more visual so i dint want to do so many mods and mucking around.
would the ccd option be better?
or going for a refractor be better?
les

[Hagar]

Really there is only a few telescopes designed for astrophotography. Your Dob isn't one of them. You will need to measure and move your mirror up the tube by quite a bit to allow a DSLR to reach focus. This is not as dificult as it sounds. Several articles are available which spell out the process.
The other option is of course an expensive one and that is to purchase a good APO refractor or a dedicated Astrograph. The Dob will work well but you will need to make the modd and you will require a Comma Corrector like a Baader MPCC or similar.
I made this modd to a 12" dobb some years ago, it only took an hour to complete, was quite simple and worked a treat.

Good luck.

[lesbehrens]

so again u agree that a refractor is the way to go?
les

[renormalised]

Much better than the dob, if more expensive.

[Hagar]

Hi Les, It really is a matter of the type of astrophotography you wish to persue. In my opinion a refractor makes a lovely imaging scope but the cost can be almost prohibitive. The use of a refractor requires a good quality scope of APO standard. These aren't cheap. If you wish to image galaxies you need a scope with a reasonable Focal length and a reasonable objective size. eg a 102mm objective as a minimum with a focal length of arround the 800 to 900 mm making it an f8 scope. If you want to capture nebulas which are often quite large you can get away with a much smaller refractor in about the 80mm objective class. Say an ED80. This scope will not be of a lot of use with small galaxies.
The fact that a refractor doesn't have a central obstruction does help in the imaging process but again a refractor is not the begining and end of it.

Quality is the next big hurdle in both glass type and general image quality. The ability to collimate a refractor is imperative to good imaging.
Glass lens type is next with FPL 53 lenses are really a minimum to give quality images without aberations and colour shift.

Cost. Quality with a refractor costs money. Takahashi, TEC and AP make some lovely telescopes for imaging but they have a similar lovely price. Cheaper versions are available from the likes of Skywatcher at a much reduced price.

In conclusion your dob will make an excelent imaging scope provided you modify the focal length to suit your camera and use a MPCC or similar. There is no need to spend big dollars on a refractor which gives a dedicated field of view for a big wad of cash.
Sounds a bit Irish I know but experiment with the gear you have and progress to specialised equipment as your experience increases and as you deside which way you wish to go down in the imaging slippery slide.
You may notice most imagers have more than 1 scope to cater for the differing focal lengths required.

The main thing you need to concern yourself with is your mount. A poor mount will never allow you to take long exposure images. A good mount like a good scope cost money, like everything to do with Astrophotography. Some compromises can be made in your scope but the mount is the most important thing to do with long exposure photography.

Keep experimenting with what you have and have a bit of fun. Hope this helps.

[lesbehrens]

hi. how would this scope go for astrophography? sky watcher 120mm x 600mm Achromatic OTA? i just want to learn first no big rush. would this be ok ?
les

[renormalised]

Great if you like B&W piccies but colours will show chromatic aberration. Although I have seen some achro's better than others. However, if you want to get into colour pics try to stay clear of achro's. The apo scopes are much better....but more expensive (always comes down to what you're willing to pay).

For an f/5 scope, the Skywatcher is one of the better ones I've seen colour piccies from. Usually, the shorter the FL and faster the scope, the worse the aberration.

[Hagar]

If you already have this scope by all means use it. You may find ip produces a lot of chromatic aberation on bright stars or the moon etc but will not resolve colour as well as an APO or semi APO scope. If you are going out to purchase this scope you would be better to wait a while until you can afford one of the ED refractors. An ED80 is probably one of the most under rated wide field scopes available at a very reasonable price. You could do a whole lot worse than an ED80.

[renormalised]

Andrews is selling SWED80's, full kit including eyepieces, carrying case etc, for $699.....and since you have an EQ6 mount, there's your piccie rig:D

[lesbehrens]

how would the ed 80mm be for visual?
les

[renormalised]

Good....see plenty in the 80mm. Maybe not quite as much as the 120 but you've got a much better pic scope there in the ED80. The difference in visuals won't be too apparent unless you start looking for really faint stuff, otherwise the colour correction and definition of the ED80 will be substantially better than the 120, since the 80 is an apo. Resolution wise there's a small difference, but nothing to be worried about.

[lesbehrens]

can u still see galaxies?
les

[renormalised]

No problem at all....galaxies, globs, open clusters, planetary nebs, ordinary nebs, stars (double, multiple...any number!!!) etc etc. Name it and you can see it. With a good camera (DSLR or CCD/Video) you'll be able to see even more and a lot fainter than you could see with your eye alone.

Under good skies and seeing, your limiting magnitude (the dimmest you can see) with an 80mm scope is around 12.7, which will get you the vast majority of the NGC and IC catalogues, lots of the SAO stars, all the planets except Pluto, many asteroids, the ISS (:)), whatever you want to look at.

[lesbehrens]

ok. u have convinced me to buy that.
thanks for your help everyone.
les

[lesbehrens]

no other attachements needed to atach a slr?
les

[renormalised]

You'll need a T-adapter and T-ring specific for your camera (T-ring, that is). You may also need an extension tube if your camera doesn't reach focus on the refractor...you maybe too short and have to move the camera back a bit. Someone with an ED80 will be able to tell you if you need one...probably not, but it's best to ask.

[AlexN]

you'll want a 2" extension tube around 50mm long to get you to focus..

Other than that, it will be great, and with the shorter focal length of the ED80, it will be easier to learn with than the 10" newt.

[lesbehrens]

great thanks everyone
les:thumbsup:

[Jeff]

Hi les,

Down the track you'll probably be wanting to add the following also:
- cheap guide scope (via dovetail bar piggy backed onto your ED80 rings)
- guide camera (eg. QHY5, or Meade DSI pro/mono)
- PHD (or similar freeware) running on a laptop to manage the guiding

If you still want to play with the dob for astrophotography now, buy the 50mm extension tube suggested below now to also reach focus visually .... then also use with your refractor later.

If you want to also use the ED80 for visual, you'll want to get a 2" diagonal also for when object are high in the sky near the zenith. Having sail that, my 10" dob does much better visually in th suburbs, so my ED80 just gets imaging gigs.

Cheers,
Jeff

[lesbehrens]

hi. yes we will see what the future brings.
les

[luka]

Regarding visual observation and ED80 I should probably point out that from my light-poluted backyard I could not see much at all. Orion nebula, for example, was just a very faint fuzz, hardly noticable.

So don't expect to see much unless you have dark skies.

[renormalised]

Les lives in Kilcoy....popn' about 1500 or so. Light pollution is hardly a problem:D:D

Living in Perth, you'd probably die of fright if you saw skies like in Kilcoy:eyepop::P:thumbsup:

You'd also do the same if a Yowie came up and tapped you on the shoulder (Kilcoy is known as the Home of the Yowie):P:D

[lesbehrens]

the kilcoy yowie statue
http://extraonline.com.au/stories/images/11007.jpg

they are real, kilcoyers see them all the time.:lol:
les;)

[TheDecepticon]

Not really. Some refractors wont come to focus either, depending on what you use to image with. You may have to use extension tubes on the focuser draw tube or shorten the telescope tube to move the focuser further up. Also, it is becoming more obvious that refractors can have as much coma as reflectors so a field flattener will be required also, and this then can change your focus point too.
Pick a scope and camera type to use, do whatever mods are required and go from there. Don't stress, enjoy the hobby and learn as you go, it takes a while to get it right!!
I am also a bit concerned that you have a low profile focuser and have moved the mirror up the tube and it still wont focus. Are you in an Astro Society where you could get some help from one of the imagers in the group?:shrug:

[jjjnettie]

Unfortunately some of the local puritans removed his dangly bits.:whistle: New ones get put back on, and they get taken again.
There must be Yowies up in the mountains though.
We get the occasional film crew from over seas trying to do a doco on them, so they must be real.;)

[lesbehrens]

hi. well i did get focus on a far away land object, but then i tried it at night it was as though the collimation was way out as i could see lots and lots of unfocused stars. i don't know what i did wrong??? because i moved the mirror up (i used longer bolts as i dont want to chop my tube), collimated it too and even tried a low profile focuser.????
thats why i am looking at a refractor to start with now thought it will be easer till i want to go to the next step again.
agin what do u think is a better scope to do astrophotography with?
les

[MrB]

Les, Andrews also has the PRO-ED80 gold tube for $479.
Tho this is for tube, rings and dovetail only.

[lesbehrens]

hi. i have seen it going to give a ring tomorrow to see if any r still in stock.
les

[bmitchell82]

As for your problem,
A- if you have used longer bolts for culmination, have you increased the spring tension to match?
B- Have you actually checked where focus is, because remember that for your eye pieces to come to focus the camera focus point is no different just where the focus pickup is.
C - Try a barlow see if you can reach focus.

you have to figure out how far away the camera sensor is from the focus point that will tell you if a low profile focuser will work, or a slight nip tuck of the tube is required.! over all, this is not a big task, just one for a steady hand.!

[telecasterguru]

Les,
I just left a story on one of your threads about reaching focus.
I have a 10" dob and use an Eyepieces Project Camera Adaptor (with or without an ep) and a 2 times barlow and focus through my dslr is great.
It works for me.

[lesbehrens]

hi i am looking at the skywatcher ed 80 or the sw 150*750mm refractor. which it the best bet for astrophotography? with my canon 450 d.
thanks
les

[dugnsuz]

ED80 all the way! The 150x750 refractor is an achromatic refractor - purple fringes around all the bright stars in photographs. Not so with the ED80 (apochromatic refractor). One thing, you'll find that around the edges of your images from the ED80 the stars will suffer from coma. This can be fixed by the use of a flattener/reducer.
Cheers
Doug:thumbsup:

[lesbehrens]

ok. cool the ed 80 is still the better one.
les

[lesbehrens]

hi. i did use a bar loe i did get focus but i didn't have my mirro adjusted up or low profile focuser in. i still want to use the 10"for visual to. thats y chopping is out + i didnt want to wreck the scope.
les

[lesbehrens]

can some one help me on this?? if i used a barlow and a reduser would i get a wider field of view or will it be no point.? would i need to use a low profile focuser to do this?
i still dont want to chop my tube.
les

[AlexN]

if you were to use a 2x barlow and a .5 reducer, your camera would be further from the imaging plane than without the barlow and reducer, however the focus point would be unchanged.. ( I think ) depending on the order in which you placed the two...

I think your best bet is to image through the ED80, visual through the 16", sell the 10" to fund a guide scope, guide camera, and a field flattener for the ED80 and you'll be set.... You'll have a great wide field imaging setup, a brilliant 16" visual scope and a BIG smile on your face.

[jjjnettie]

I agree with you totally on that Alex.
And Lesley, if you ever need anyone to look after your babies, I'm always here to baby sit.

[lesbehrens]

ok. thanks guys.
les