Guide Camera or LP Filter?

[all-on-black]

I was looking at getting a guiding system for my setup. I have a skywatcher 150pds on an EQ5 go to.

I've got a cable coming to control via EQMOD, so will be using alignmaster to get my polar alignment bang on (I hope) to get slightly longer exposures.

However, I know that a guide scope ultimately will be the best way to get longer exposures.

BUT, I would also like a LP filter for my DSLR.

Finder guider set up - approx £200.

Filter - Approx £150.

I have a fair bit of light pollution in my area, and i've found that trying longer exposures, even at iso100, gives me an image with a fairly bright sky.

So, would it be more of an advantage to get a filter, and stick with 1 minute(ish) exposures for now, or get the guide set up and hopefully be able to process the image for a darker finish to the sky?

Please help, thankyou!

[astromerlin]

Faced with the choice, I'd go with the LP filter first then try to pick up a secondhand finderscope and a ps3 eye webcam can do 2-3sec exposures- very noisy but I used one for a while with good results.

[Pete Presland]

i would probably agree with the filter, when you say very bright images, is this after a 60 sec exposure at ISO100?

[Astrosurf]

The filter too! But if you're part of an astro group and can go out regulalry to a dark site then I'd go with the guiding option! Interesting suggestion about the PS3 Eye, John.

[RikM]

Guiding is the key to better images. You can get a Skywatcher LP filter for not a lot of money and that will give you a good start to reduce unwanted orange glow but TBH you can get rid of phenomenally bright background in post processing. You just need enough exposure time to be able to tease your object out from the background and for that you need exposure. There is a huge difference between even 1min and 3min subs. When you can reliably capture those subs, and not have to ditch 30-50% due to poor tracking, your image quality will take a big jump forward.

How you process the images is also key to getting good sky background.

[lensman57]

I was looking at getting a guiding system for my setup. I have a skywatcher 150pds on an EQ5 go to.

I've got a cable coming to control via EQMOD, so will be using alignmaster to get my polar alignment bang on (I hope) to get slightly longer exposures.

However, I know that a guide scope ultimately will be the best way to get longer exposures.

BUT, I would also like a LP filter for my DSLR.

Finder guider set up - approx £200.

Filter - Approx £150.

I have a fair bit of light pollution in my area, and i've found that trying longer exposures, even at iso100, gives me an image with a fairly bright sky.

So, would it be more of an advantage to get a filter, and stick with 1 minute(ish) exposures for now, or get the guide set up and hopefully be able to process the image for a darker finish to the sky?

Please help, thankyou!

Hi,

LP filters are helpful but by no means 100% effective, I have 3 of the expensive variety and a 2" UHC-S type filter and all these have their weak points. You should also have a look at the type of the pollurion that you have, we now have a new menace in the form of the white light pollution against this no filter is effective as they were for Sodium type of pollution.

If you have access to a dark site then this  is the better of all the options but I do understand the trouble of packing and travelling. You could try an inexpensive LP filter such as the SW  LP filter first and see if this makes a tangible difference to your exposure times, from there on you can decide wether it is worth going for an expensive one. As for guiding, this again depends on  your local sky  light pollution and background skglow. If your limiting exposure is about 120 or  so seconds then as you have suggested an accurate polar alignment  with good balancing may be sufficient there is no point in guiding for 300s if all you add to the capture is LP and skyglow.  I used to get about 120s on my old EQ5 Pro SynScan with good alignment and proper  balance using an ED 80 without guiding. Hope this helps.

Regards,

A.G

[all-on-black]

i would probably agree with the filter, when you say very bright images, is this after a 60 sec exposure at ISO100?

No its more like 90 seconds or more really. Obviously the longer the exposure the worse it gets

[all-on-black]

I think based on your responses I will get my mount aligned using align master and try some 2 minute exposures and see if i can get rid of the light pollution in processing.

If i cant then itll be a LP filter, if i can then itll be a guide scope set up!

[lensman57]

I think based on your responses I will get my mount aligned using align master and try some 2 minute exposures and see if i can get rid of the light pollution in processing.

If i cant then itll be a LP filter, if i can then itll be a guide scope set up!

I think that you are on the right track here. If need be an SW LP filter is about £36.00 for a 2" one, you could always resell this quite easily for about £20.00 ~ £25.00 afterwards.

A.G

[all-on-black]

Ive actually already got the 1.25" one, completely forgot as i dont do much visual stuff. But i remember it being pretty good. May dig it out next time and see if i think it can be beneficial to get a good one for the dslr.

Either way ill probably end up with both the filter and guide set up very soon but dont tell my girlfriend!!

[Physicist13]

The question to ask is, what is limiting you taking longer exposures. Light pollution (at what exp time does the light pollution saturate your images )? At what exp time does trailing (at a level you decide is too much) occur? This then determines which route will be best for you.

P

[Astrosurf]

I was told by FLO that you can't use those LP filters with Canons (or is it DSLRs generally?!). You would need the Astronomik EOS Clip-in filter but they're a lot more expensive. I have a second-hand one and it's very good. It can cause halos around stars though. I hope I'm not giving you duff gen! Ask FLO.

Alexxx

[lensman57]

I was told by FLO that you can't use those LP filters with Canons (or is it DSLRs generally?!). You would need the Astronomik EOS Clip-in filter but they're a lot more expensive. I have a second-hand one and it's very good. It can cause halos around stars though. I hope I'm not giving you duff gen! Ask FLO.

Alexxx

You can not use it inside the camera but it can be fitted to a 1.25" nose piece and inserted into the visual back. If an FF/FR is used matters get complicated as a 2" version is required to be screwed onto the end of the FF/FR.

A.G

[RikM]

I use a 2" SW LPR filter screwed to the front of my coma corrector.

[Astrosurf]

Thanks Rik, A.G. Would the nosepiece with the filter cause trouble with achieving focus? I can't reach focus with my SW coma corrector (useless thing) so couodn't use a filter as well. What's FF/FR??

[lensman57]

Thanks Rik, A.G. Would the nosepiece with the filter cause trouble with achieving focus? I can't reach focus with my SW coma corrector (useless thing) so couodn't use a filter as well. What's FF/FR??

This is interesting as some people claim  that they can reach focus with the DSLR and the 200psome say that they can not.  

A.G

[all-on-black]

Thanks Rik, A.G. Would the nosepiece with the filter cause trouble with achieving focus? I can't reach focus with my SW coma corrector (useless thing) so couodn't use a filter as well. What's FF/FR??

FF = Field Flattener

FR = Focal Reducer

This is interesting as some people claim  that they can reach focus with the DSLR and the 200psome say that they can not.  

A.G

I think it depends on the DSLR, some bodies are bigger than others so would probably have more depth, thus moving the sensor even further away from the focus point.

The question to ask is, what is limiting you taking longer exposures. Light pollution (at what exp time does the light pollution saturate your images )? At what exp time does trailing (at a level you decide is too much) occur? This then determines which route will be best for you.

P

Depends on the night really, with the moon out I guess exposures of 90sec plus are out of the question, but on a dark night I reckon 120sec could be achievable fairly reasonably.

As for star trails, i've been able to get a max of a minute before star trails start. I have an EQ5, so the clocks are useless, and I haven't centered the polar scope. Now i'm connected via EQMOD I can get a much better alignement using alignmaster ( I hope!! ).

More testing is needed really, before I can make a decision. Which is fine because I have 2 holidays to pay for, a new set of tyres needed for the car, as well as a service! 

[RikM]

This is interesting as some people claim  that they can reach focus with the DSLR and the 200psome say that they can not.  

A.G

It depends on both the camera and the scope. I have newer than 2010 150P and 250PX both with standard single speed focusers and both of these reach focus just fine with a Canon 1000D and either a MaxDSLR 2" nose-piece or a Baader MPCC type II. 

The old blue tube SW Newts generally don't reach focus with DSLR's, the ones with 1.25" focusers don't reach focus and there seem to have been a short run of 'black diamond' 200P's that were the same as the blue ones but with the new paint job. These also don't reach focus. Newer 200P's reach focus fine, at least with Canons, even the single speed ones. You do need a low profile nose-piece or coma corrector though.

[lensman57]

It depends on both the camera and the scope. I have newer than 2010 150P and 250PX both with standard single speed focusers and both of these reach focus just fine with a Canon 1000D and either a MaxDSLR 2" nose-piece or a Baader MPCC type II. 

The old blue tube SW Newts generally don't reach focus with DSLR's, the ones with 1.25" focusers don't reach focus and there seem to have been a short run of 'black diamond' 200P's that were the same as the blue ones but with the new paint job. These also don't reach focus. Newer 200P's reach focus fine, at least with Canons, even the single speed ones. You do need a low profile nose-piece or coma corrector though.

Hi Rik,

Is this also true for 150P , if so this can be a 1100significant saving in cost for me as I intend to get one just to have a Newtonian for imaging with my Canon 1100d and an SW CC?

Regards,

A.G

[RikM]

I don't know how much the SW coma corrector shifts the focus point in. Being effectively a 0.9x reducer as well I would expect some inward shift in focus. Certainly the MPCC-II (which doesn't change the focus point) is fine with the 150P and 300D, 1000D and 1100D as I've used all of those (1000D being my favourite). I would expect all the EOS cameras to works but that is an assumption on my part.

[Astrosurf]

This is interesting as some people claim  that they can reach focus with the DSLR and the 200psome say that they can not.  

A.G

Only witrh the CC, otherwise there's no problem. I think the SW focusing tube has change in design over the years. Mine's a good few years old and a blue tube.

I hope I'm not hijacking this post and that this info will be useful!