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SW150p (Reducer for imaging DSO??)

t0ny

By t0ny
in Getting Started With Imaging

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t0ny

t0ny

Posted
Posted

Hi,

I would like to give imaging a go, but I believe my scope is far from ideal. i have been reading about Reducers and wonder if this might help make this scope better for imaging whilst I learn the ropes?

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Ant

Ant

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The 150P is not a bad scope for imaging.

It is already a quick scope at F/5 - I doubt you'll find a reducer to make it any faster (and indeed not sure you'd want to). The one issue with these Newts is Back Focus (not having enough inwards travel on the focuser) when adding in a camera.

I know that various models exist that have this issue partially resolved, certainly when I had my 150P (old blue tube model) I had to move the main mirror up the tube to reach focus with a dSLR.

So I see that you have a dSLR and a webcam. For Lunar and planetary imaging you want the opposite of the reducer (a barlow). This will increase the effective magnification and make the planets and moon bigger on the chip. You should be good to go on that front, pop in the webcam and start with the moon.

For the dSLR, get a T ring (http://www.firstlightoptics.com/adaptors/t-rings.html) for your model and this should screw directly onto a camera thread on your focuser - you'll need to unscrew the EP holder to reveal the thread.

Failing that, add one of these (http://www.firstlightoptics.com/adaptors/flo-2-inch-t-mount-camera-adapter.html) and this will go into a 2" standard focuser. But this is where the back focus *may* become an issue.

Cheers

Ant

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t0ny

t0ny

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Thanks Ant,

All my gear was purchased a few years back, but the arrival of some little ones meant it had to stay in the garage.

It has recently been dusted off and I hope to get further with it this time round.

I have a TRing for my Nikon which I used on the Moon once.

I'll try to see if I can Focus. Can I try this in the day time or does it work differently for 'up there'? 
I have a Bahnitov Mask too, but did not get anywhere with it.

Thanks

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Ant

Ant

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If you can find something a long way away (1/2 mile or more ideally) then daytime focusing should give you some idea, remembering that infinity focus will be a fraction closer.

Now that I didn't know :)

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Nathan_Pembs

Nathan_Pembs

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I tried using a reducer on my 150P, I found there wasn't enough inwards travel with the focuser.

Also the coma that all Newtonians suffer from was made even worse, making the fov extremely distorted. Only a small part in the centre was as it should be.

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Chris

Chris

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The Skywatcher coma corrector has a small reducing effect of .9x so it reduces the 150p from f/5 to f/4.5, plus removes coma. They require an M48 ring instead of the T-ring. If you have the black 150p which reaches focus not the older blue model I would recommend it for imaging.

Heres the link, the M48 ring is also at the bottom of the page:

http://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html 

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t0ny

t0ny

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I have the Black 150p so that's good news i think!

Will I still not be able to get a focused image without buying the M48 ring thing? 

If am going to spend any more money I'd ideally put it towards a used Canon DSLR (rather than my Nikon) or an 80mm Refractor as everything I read says that's what I should have!?

Thanks for your help everyone!

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Lonestar70

Lonestar70

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I have the Black 150p so that's good news i think!

Will I still not be able to get a focused image without buying the M48 ring thing? 

If am going to spend any more money I'd ideally put it towards a used Canon DSLR (rather than my Nikon) or an 80mm Refractor as everything I read says that's what I should have!?

Thanks for your help everyone!

Hi Tony,

Unfortunately you would need the M48 camera adaptor regardless of either Nikon or Canon... your present Nikon T2 camera adaptor has a different thread (M42) and won't fit onto the Skywatcher Coma corrector.

The same would apply if you had a Canon T2 camera adaptor.

It would not necessarily be wasted money since you would also need this adaptor if you ever get an ED80 with it's Field flattener/Focal Reducer... and the M48 size will give you less vignetting in either scope set-up.

Unfortunately there are, as yet, no one size fits all common industry thread standard for astro bits.

Another reason Astrophotography can get expensive I am afraid... but we all share the same problems.

Good luck and clear skies.

Sandy. :grin:

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Chris

Chris

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I have the Black 150p so that's good news i think!

Yes I can confirm that is good news from a DSO imaging point of view :)

Will I still not be able to get a focused image without buying the M48 ring thing? 

If am going to spend any more money I'd ideally put it towards a used Canon DSLR (rather than my Nikon) or an 80mm Refractor as everything I read says that's what I should have!?

The M48 ring just enables you to connect connect your camera to the coma corrector, the usual T-ring doesn't fit this coma corrector. The Baader coma corrector will fit your existing T-ring but it costs 40 quid more. The Baader is a slightly better coma corrector though. The Skywatcher coma corrector plus M48 is the more budget option but still works very well. Some report reflections around very bright stars but this will be the minority of objects that you image.

The 150p is an excellent scope for DSO imaging, no better or worse than a refractor just different. They both have strengths and weaknesses. If you do go for a refractor its needs to be ED at the very least, not a cheap achromatic refractor or you will get very bloated stars from the chroimatic aberration. Reflectors such as the 150p give perfect star colour because mirrors focus all the wavelengths at the same point. 

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t0ny

t0ny

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Ok, time to embarrass myself.

As it stands I can connect my old Nikon DLSR direct to my SW150p using the TRing. Ignoring focus for a minute, I can take snaps of the night sky.

So, in simple terms why would I need to throw a coma corrector into the mix? 

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Chris

Chris

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You don't absolutely need one, but the Skywatcher coma corrector is the only thing that will help you speed up you scope a bit (reduce focal length) whilst improving your image with a flat field as a bonus. 

I was just trying to think in terms of your original question whilst stearing you towards an item that most imagers end up getting for there reflectors :)

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t0ny

t0ny

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Thanks starfox I was under the impression the scope would be useless for imaging so wondered if there was anything I could do in the short term before getting an 80mm refractor.

It's nice to know I might be able to get something and also improve it with the corrector. I just got an HEQ5 Pro, so not allowed to spend anymore until the space dust settles!

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Chris

Chris

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I'm not sure why you thought the 150p would have been useless for imaging? On a budget I think its probably one of the best imaging scopes you can buy :)

Certainly unguided with a DSLR you would likely get better results with a 150p than an ED80 because its optically quite a bit faster, f/5 verses f/7.5 natively. I think you would need roughly half of the exposure time with the 150p compared to the ED80 to gain the same amount of signal. DLSR's suffer from noise which builds up over time, this makes fast scopes attractive to DLSR imagers. f/5 is perfect because if you go much faster they become very difficult to collimate. 

Oh nearly forgot! congrats on the new mount, its a very good choice for imaging :)

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Uranium235

Uranium235

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Indeed..... small newts are fun ;) I have both the newt and frac, but only one gets used regularly.... and it aint the 80ED!

Its worth getting the SW coma corrector if you cant stretch to a Baader, the SW reduction factor can be tuned so it will reduce by more than 0.9x through increasing the spacing distance by couple of mm - the trade-off being worse corners.

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Chris

Chris

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Yes Tony thats the one, The ST80 is a great scope for many reasons.

- guidescope

- Super finder

- widefield grab and go scope

Long standing SGL member Gina has recently shown that you can even image in narrow band with them!

Heres a good link to some small mods that can be done to improve the ST80 on cloudy/rainy nights:

You should be able to buy a dovetail bar which can attach to the top of the 150p tube rings. Then you can bolt the ST80 down onto said dovetail. I'll let someone else recommend a specific dovetail as its not something I've personally done, yet.

I know what you mean about the clouds, I looked out side when getting the kids ready for bed and it was clear, ran out with my binos to try and catch comet Lovejoy once the kids were alseep and it was thick cloud ! :(

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