Next Upgrade - EAA or New Scope?

[Starpaw]

Hi,

I'm currently using a Celestron 102 SLT, and whilst I love this scope, particularly for its widefield views and portability, I'm feeling the need to upgrade my setup.  

I have two ideas.  First is a Celestron C6 or 150 Mak mounted on the Skywatcher Star Discovery goto mount (goto is almost essential for me in London) for planetary, double star and small DSO observing (globulars, galaxies etc.).  Second idea is a bit more radical.  Instead of buying a new scope altogether, I have thought of getting the Lodestar X2 and diving into the realm of EAA.  The latter seems to make a lot of sense since by upgrading I am hoping to see more details in objects and punch through the horrid light pollution of London.  However, I'm not sure if it would take away some of the  fun of observing (messing around with eyepieces etc.). So, what do you think and do you have any alternative ideas?  I should mention that I do not have a garden (portability is important) and my budget would be roughly around £500-£600(I intend to purchase second hand items where possible).  Thanks for your thoughts in advance.

[rl]

Hmmmm...I'm not really sure what EAA means. I suspect the only difference between EAA and full-blown imaging comes down to the quality of the mount and guiding which will determine your maximum exposure time. Please correct me if I'm wrong on this. Maybe you need to define "portable" in your context. Does the whole shebang have to fit in a tesco carrier bag (other bags are available) or a land rover (ditto 4wds)? How far is your intended site? If you have to carry the whole lot on a bus then you might be down to a skywatcher photographic mount and and a canon 1100d with a 50/ 135 mm lens, with a 70mm apo if you're tracking's good. Actually you could do quite a lot with that...

Narrow band ap might be your best bet in central london but the filters are a lot more expensive and I'm not sure how well they work in widefield situations. You will certainly need a UHC style passband as a minimum. 

I was a student in london for years....picking a good site meant in reality choosing the most easily filtered least obnoxious form of light pollution....looking for parks with low pressure sodium lights. Sadly they're going out of fashion. 

Planets area good option even in london.

Let us have a few more details.

Best of luck

RL

 

 

[Starpaw]

EAA stands for electronically assisted astronomy.  In this context, the Lodestar would be used almost like a video camera with a 5-30 second delay i.e. 5-30 second exposures.  The chip it uses is super sensitive, so from what I seen it seems like good results are achievable when used in conjunction with the Lodestar Live software, which allows you to adjust certain parameters on the fly, and stack images on the fly as well.  So, I don't really see this as a form of imaging, rather as an aid to observation.  I've also watched videos where this is done with fairly modest gear (6 inch SCTs on goto mounts), so big HEQ5s and apo scopes do not seem to be necessary at all because you're not doing long exposures and aiming to take the most beautiful and technically proficient images.  Rather I think the goal is to see more detail e.g. spiral structure in M51.  I guess the best way to understand what I am getting at is to have a look at a video on Youtube:

I don't know if this is the case or not, but I was thinking going down this route would almost be like doubling the aperture of my current scope?

As I don't have a car, portable for me would be all my gear fitting into my wheelie bag, which is around 75cm long, and backpack.  I use this for my current setup.  This is why I was thinking the C6/150 Mak as I could easily fit the OTA into my backpack and put the mount in the wheelie bag.  I'm just unsure as to whether the 2 inch aperture upgrade, not taking into account the secondary obstruction, is going to leave me underwhelmed or not.  I should add I regularly go to Norfolk (I lug my gear on the train) where the sky is very dark in places, so maybe this extra two inches would be more noticeable in that context.  I have also considered the C8, but the problem is the size and the cost of the mount that is needed to support it.

 

[rl]

Thanks for the video link...interesting stuff. I still think its a matter of semantics...AP with short exposures! A lot of people do AP with 30 second subs it the guiding 's not too hot. Ultimately if you're going to get the best out of it you will end up addressing all the same issues as AP but with maybe less rigorous solutions in view of your budget. 

If you can stack images and subtract dark frames then this looks like having a lot of potential. Your photo looks like my pc screen used for full-blown imaging....it's just like setting up and framing a target with some short exposures before taking the real one. 

How well is your C6 option optimized to the chip size for the targets you want to look at? It's a fairly slow scope. At this level the step from 4" to 6" is still worthwhile visually (f-ratio not important for visual, mag only), especially on DSOs. It's roughly a 1 magnitude improvement for the same magnification. Trouble is the same applies to the background. But for a camera which integrates the light on a sensor the f-ratio is important. 

You may well have a point about effectively doubling the aperture if the software magic does its job bumping up the contrast. 

I hear you about not obsessing about the most technically elegant images; I'm always grateful to get anything halfway reasonable!

It's so easy to mess up when going portable.

Anyone else got direct experience of EAA?

 

rl

[Starpaw]

I guess the main difference I see is that EAA is more instantaneous i.e. like looking through the eyepiece and without  post image processing (someone is probably going to come along and call me a heretic for that comment! ).   That is something which is appealing to me as I would lack the patience for processing etc.

My current scope is F6.5, so it would be ideal for EAA I think.   I should clarify I don't have a C6.  If I were to get one, it would be for visual use as I wouldn't be able to get the camera as well, plus the focal length would be kinda ideal for a lot of observing I do (double stars and planets in the city, small DSO in countryside).

I'm not overly bothered by CA, so another achromat would be another option.  A 120 Evostar seems to have quite a versatile focal ratio (F8).  Given the central obstruction of a mak/SCT (roughly an inch of aperture by area), is a 5inch  refractor the equivalent of of a 6 inch catadioptric? Or is my logic flawed here? 

An SW Evo 4" ED at a good second hand price wouldn't be a bad idea or would it? Despite its length, I could transport this in a padded scope bag inside a 1.4 metre fishing rod bag that I have and sling it over my shoulder? Perhaps a scope like this this would offer ability to ramp up magnification?  I've noticed when looking through some apos at star parties they can take high mag with little image degradation, but then again they were extremely good apo scopes with Ethos eyepieces...

It's difficult to make my mind up!  I can be a bit of a luddite and like to keep things simple, so the old school way of observing has some appeal too.  But sometimes I like to do something different.  Sorry for thinking out loud!  I will probably have to flip a coin if I am to avoid going insane...

[rl]

I think most people would concur that refractors deliver the most bang per inch in this size range and they have the big, big advantage of not requiring collimation. The last thing you want to be doing is twiddling mirrors in some dark damp field. You will have enough problems with cables, flat batteries etc. Combine that with fairly short cool-down time and they're always a winner for portable use.

My main scope for 15 years was a 130mm f/10 doublet refractor that went everywhere in the back of a small car. You can do a lot with this sort of size. It was a standard achro (made by John Owen) at f/10 and had a minor amount of CA which never really bothered me. I've also had a skywatcher 120mm short focus (f/5) simple achromatic refractor which was brilliant for widefield visual use but the CA really was too much; planets were washed out. My GT81 easily outperformed it on Jupiter. It also had a lot of field curvature which was an issue when trying to image.  I've owned several catadioptrics and been disappointed with all of them . However, I've looked through some of other people's which have been great. They do seen quite variable in quality. Refractors-especially the quality ED ones- seem rather more consistent in my experience. The 120mm f/8 has a large fanbase but might be a bit heavy.

I'd be very tempted by a 4" ED. A short focus one hits a good sweet spot for capability/ portability provided you really can carry it along with all the other stuff. It might be a better choice for purely visual use. If you're also carrying an equatorial mount, camera, laptop and batteries it might still be a bit big. In your position I might well be thinking a bit smaller, say 80mm. My GT81 would be about as much weight in the OTA as I'd want to carry personally, but that's a heavy 80mm so a light 100mm might still be practical.  

The great thing about AB+S is that it's so easy to change your mind and try something different without losing a fortune! I used to keep kit for ever but have been quite promiscuous in my astronomical interests since discovering that site...........it's on the "favourites" list on my work pc which will get me into trouble one day.

RL

[SkyGibbon]

I would go the EAA route. A decent camera is around the same cost as 1 higher end eyepiece. I live in a white zone myself and can view much more, and view things undetectable through an eyepiece because of the light pollution. As long as you have the monitor /comp already, your only cost is the camera. Almost all software for EAA is free.

 

I still view targets that are visible through an eyepiece though. Solar system, brighter DSOs, doubles, etc.