DSLR Deep Sky

[JohnSadlerAstro]

Just a few questions about imaging with a DSLR:

1: how can I find out if there won't be enough inwards focus to bring the cam into focus? 

2: how can I find out what the cam's FOV will be in my scope?

3: what sort of  objects would I be best to target with a modded DSLR, perhaps a 1000D?

Thanks

JOHN

[PeterCPC]

1. Try it

2. Use http://astronomy.tools/

3. Modded are best with Nebula but you can use them for all DSOs.

Peter

[carastro]

1. It depends which scope you have.  If you have a Newtonian not adapted to astrophotography you might have problems getting focus with any camera.  With a refractor you should have no problems.  

Otherwise google your scope and see if any-one is imaging with a DSLR.

If you tell us what scope you have then maybe some-one will know the answer.

2.  I use http://www.12dstring.me.uk/fov.htmfor this.  Just put in your scope and camera (or closest to it if it's not listed).

3. Brighter targets will be fine, if the camera is modded those with Ha will come out well.  Dimmer targets will also come out but won;t show a lot of detail.

Carole 

[hjw]

Hi John,

to achieve focus is dependent on the scope. Since you are interested in the inward part I presume you have a reflector. If the reflector was designed for observations focus might get problematic. Others are designed for astrophotography and focus will not be a problem. I have a refractor and need a 50mm extension tube (or better a field flattener) to achieve focus.

I use stellarium to fiend my FOV. In the top right hand corner is a field to enter sensor size and focal length etc. The software then draws a frame on the screen of what will fit in your picture.

Nebulas and clusters are easy. Galaxies are a mixed bad as some are very faint. Also depends on whether you are guiding or not.

If you want, you can have a look at my images (see signature). They are all done with an un-modded Pentax K-30.

Clear skies!

HJ

[JohnSadlerAstro]

1. It depends which scope you have.  If you have a Newtonian not adapted to astrophotography you might have problems getting focus with any camera.  With a refractor you should have no problems.  

Otherwise google your scope and see if any-one is imaging with a DSLR.

If you tell us what scope you have then maybe some-one will know the answer.

2.  I use http://www.12dstring.me.uk/fov.htmfor this.  Just put in your scope and camera (or closest to it if it's not listed).

3. Brighter targets will be fine, if the camera is modded those with Ha will come out well.  Dimmer targets will also come out but won;t show a lot of detail.

Carole 

I have a 130mm f/7 900mm focal length reflector.

[Knight of Clear Skies]

I have a 130mm f/7 900mm focal length reflector.

People will need the model please as it's the design of the tube and focuser that will determine whether it can reach focus with a camera or not.

[JohnSadlerAstro]

Its a Skywatcher 130mm EQ2 f/7 reflector model. These are the specs:

SKYWATCHER EXPLORER-130 TELESCOPE
130mm (5.1") f/900 Newtonian Reflector 

• Diameter of Primary Mirror: 130mm
• Telescope Focal Lengh: 900mm (f/6.92)
• Aluminium Tripod with Accessory Tray
• 30% more Light Gathering than 114mm
• Tube Dimension(dia. x length) 17cm x 83cm

I'm not sure whether Skywatcher still make this one; the 130mm telescope on their website is the 650mm focal length version.

[D4N]

Skywatcher make several 130mm reflectors, the 130P-DS is the one designed for using with a DSLR. The others struggle with inward focus and the focusers are not strong enough to take the weight of a DSLR.

Unless you have the RA motor for the mount then the DSLR will not be able to do much anyway, the mount needs to track the target during exposures for deep space imaging.

You can however do planetary imaging well with that scope. A simple webcam modified to remove the lens and inserted into the focuser will be great for the moon and planets.

/Dan

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[JohnSadlerAstro]

Yes, I do have an R.A. drive, but I see what you mean about weight being a problem--the focuser barrel isn't very strong. I think I may opt for the Altair GPCAM as a second-best. I am already doing a little bit of lunar and planetry imaging, as I have a Orion SSSSCI 4 which I use in conjunction with the motor drive.

[D4N]

It is possible to fix the focuser if you don't mind a bit of DIY.

First thing to do is undo the screws on the rack and pinion and clean off all of the skywatcher grease (this stuff is like glue!) replace this with some silicone grease. This will make the focuser a lot smoother and easier to get accurate focus on.

You can make the focuser knob bigger too, either attach a jar lid to it or a lolly pop stick. This will allow you to make the smaller movements that are required to get good focus on the camera.

Fixing the weakness of the focuser is harder, I drilled two holes 120 degrees either side of the rack and superglued some M8 nuts to the outside. Now I can just tighten some M8 bolts into those nuts and it locks the focuser preventing any movement or sag when it is under weight. I glued some rubber pads to the bolts so they don't scratch the tube.

If you do decide to drill the focuser to fit locking bolts then I would suggest removing it from the OTA first to avoid risk of debris falling in, be sure to point the scope down a bit when you do that so if you drop a nut it falls out rather than onto the primary mirror.

/Dan

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[theghettostylus]

I had the skywatcher 130 spherical mirror not the parabolic, and couldn't archive focus because of not having enough inward travel. I am using the 1000d unmodified and it works very well so far but I'm now using it with the skywatcher 150p and have plenty of inward travel. If yours is the spherical mirror then you will be stuck for inward travel. I even cut my focuser down and had to remove so much it was useless.

[Jokehoba]

I have the Skywatcher 130P/650mm and originally could only achieve focus with a x2 barlow due to the lack of inward travel. After a year or so, in a fit of madness, I took an angle-grinder to it and shortened the tube so I could achieve focus at the native FL. It's worked out quite well! Still, I realised I needed a SW coma corrector which meant shaving off another 25mm...

Like HJ I generally use Stellarium since you can configure several scopes, barlows/FRs, and sensors. You can also rotate the FoV to check framing.

Ron Wodaski's CCD calc - http://www.newastro.com/book_new/camera_app.html- is also handy.

John