Shooting with a reflector

[poider (Peter)]

G'day, I have a 6 inch with a 750mm tube newtonian reflector, It is only a cheapie but I am going to have a go at using it for Astrophotography.
Firstly can any body tell me what the equivalent refractor would be in size, Is the six inch reflector the equal of a 60mm refractor with a 600mm tube?
Now as for taking the photos, I need to get a T piece and a dslr ring to attach the camera to the scope, but I am confused as to what the purpose is,
To attach the camera I will need to remove the eyepiece, but then wouldn't I just be taking an unmagnified photo as the magnifiying part of the scope will not be there??
Does the mirror play any part in the magnification of the image???
Peter

[Atmos (Colin)]

Shooting with a reflector is the same as a refractor. The focal length is what determines the magnification factor.
You do need a T ring to connect your camera to the telescope, it goes in the same position as what the eye piece does, it replaces it. This is what is known as Prime Focus Imaging, where the telescope becomes the prime lens for your DSLR.

[RobF (Rob)]

You'll probably have a lot of trouble getting sufficient backfocus to take pics. Point it at the moon tonight and put a piece of paper where the eyepiece normally goes. The image plan (point where you see the moon projected on the card) is where your camera sensor will need to be.

Lots of threads on here about cutting down the tube of reflectors to bring out the focal plan, or putting on a low profile focuser. Some modern Newts allow you to attach T ring natively without surgery.

Good luck!

[thegableguy (Chris)]

By far the easiest solution is a 2x Barlow T-adapter. It reaches focus easily and adds a fair bit of magnification. Worked a treat on my 8" Dob reflector. Celestron make them; think I got mine from Australian Geographic.

Having said that, the only things you'll be able to shoot without a tracking mount are planets (which is why the magnification of that Barlow is essential - planets are reeeeally small). Darker objects are impossible without long exposures - take it from someone who tried!! I sold my Dob and spent way more than my wife thought was reasonable on a mount and small refractor...

[thegableguy (Chris)]

Found a link. (You can ignore the one bad review.)

http://www.ozscopes.com.au/celestron...t-adapter.html

You'll still need a T-ring for whatever DSLR you're planning to use.

[poider (Peter)]

Can anybody please tell me what this is used for on my 6 inch newtonian reflector

https://www.flickr.com/photos/529918...posted-public/

[Mickoid (Michael)]

Originally Posted by poider

Can anybody please tell me what this is used for on my 6 inch newtonian reflector

https://www.flickr.com/photos/529918...posted-public/

The gear wheel connects to an electric motor which turns the RA axis for tracking an object, you can buy one on eBay for around $80. The lever is used when the motor is attached, to disengage the gearing so the RA can be moved manually. They serve no purpose without the motor.

[poider (Peter)]

Thank you all for the responses

[poider (Peter)]

Pardon my niavity but would'nt we need two motors

[Atmos (Colin)]

To track an object you only need a motor in the RA axis. As the Earth rotates in one direction (doesn't wobble or do what Mars does) we only need one motor

[poider (Peter)]

so I point the latitude scale at my latitude, then point the Declination circle at 90, the point the polar axis at the celestial south pole and I should be able to use just the one wheel to track an object.
Is this correct?
Peter

[RobF (Rob)]

What would you be trying to shoot Peter?

[Mickoid (Michael)]

Sought of. Like you said, set your latitude on the latitude scale, make sure your mount is level but try to align the RA axis so that it's pointing to True South. You can use a compass to get a rough alignment by standing behind the EQ mount and sighting it toward where it is pointing to south. This is magnetic south so you will need to adjust the bearing to True South. Where I live in Melbourne, that equates to 11 degrees east of south, it may be a different bearing where you are. You'll have to research that one. If you have got the mount close to pointing south but need to make those adjustments to True South, don't move the tripod legs, just loosen the nut under the mount and rotate the polar axis whichever way is required. This will save relevelling the mount and all you have to do when adjusted is retighten the nut under the mount again. Hope this makes sense.

[poider (Peter)]

I would like to shoot the planets, jupiter, Saturn and Mars, and a few clusters and nebulae if possible

[RobF (Rob)]

Just be aware you probably won't be able to "track" more than 30secs at a time.

Planets may be fine with an iPhone or camera at focal plane with very short exposures of few secs of less. Most of the fantastic planetary shots you see are lots and lots of very short exposures from fast sensitive cams.

Nebs - will be limited to the very brightest - e.g. M42, Eta C, but may get a decent result with fair degree of pain.

Heck, any astroimaging involves copious amounts of pain.

[poider (Peter)]

Thank you Rob, I do realize that there are going to be many frustrations and disappointments. and have a little experience with night photography.
I will persist and when I get some shots I will post them, they probably won't be much but I will post them anyway.

[RobF (Rob)]

[poider (Peter)]

Thank you Michael, I had a quick go at it tonight, after setting the declination and latitude last night, I went out to look at Jupiter and was amazed that I could track it with just the one control wheel.
But then I tried to get to Saturn which is almost right above us at the time and found I had to loosen some clamps and turn it that way.

[Mickoid (Michael)]

Peter, that's right, you'll have to loosen the RA and DEC clamps to move to a new object but once you centre that object in the FOV just tighten the clamps and it should enable you to track again using the RA slow motion control. You shouldn't have to move the tripod once you've polar aligned.