Astro photography equipment requirements for the new boy?

[mothershipuk]

Hi Guys, I have slowly been trawling through the forum to try to find advise on a few things I may need in order to get some good pictures of the stars and deep sky objects so I can prove to my wife and friends I am not using the scope to look at Mrs Perkins down at number 42 even though she has some objects worth photographing !

I am new to astronomy and telescopes so would like any advice on recommendations for the following items please....

1. Some sort of 'dew control system' ? I have read a little about the benefits of a temperature sensing kit (kendrick D10) or the Dew buster. I used my scope a couple of nights ago (in my back garden as always) but was attacked by the dew monster and had to come in after only a few hours. Is there anyone out there who can guide me on this one?

2. A 'wedge' of some kind? Again I have read a little about them but if I dont get one I guess I wouldnt be able to take long exposure pictures? I have bought a dsi pro with filter slide thingy but fear my lack of knowledge at the moment means I am not even getting star pics. (sigh)

3. What Filters? With the telescope I got a few meade colour filters but have been reading about a filter called Hydrogen Alpha filter that enables you to get good nebulae pics.

The term 'all the gear and no idea' springs to mind or 'running before I can walk' but I have been bitten by the bug and am determined to learn learn learn although I could do with some advise please.

My gear:

Meade LX90 10” (2007) Dsi Pro Meade 4000 ep kit

Meade 6.7mm UWA

Televue Ethos 13mm

Televue Ethos 8mm

5 X Telextender

WO Dieletric diagonal

12mm Iluminated Reticule

Dew shield

[Sam]

What kind of camera have you got?

[mothershipuk]

Hi there,

I have a meade DSi pro and thats it! Is it any good?

[beamer3.6m]

The DSI is a good camera. I personally use a modded Toucam which I think is just as good, except you get the benefit of the Meade software and the ability to automatically take flats and darks as I understand.

You should be able to get some decent images but remember that the field of view with such cameras is very narrow. On my Explorer 200 the Toucam is about the same mag as 6mm eyepiece so I would recommend that you test it out on the moon or if you must try a DSO then something big like M31 so that you can be sure that you have it on the chip.

For dew have you tried a dew shield from FLO or a cheaper alternative is a camping mat cut to size and slipped onto the end of the scope.

Should hold dew at bay for a while, at least it prevents it totally on my Newtonian.

[narrowbandpaul]

as a start, a chip with a good sensitivity will be good. Once you learn more and more you will realise that sensitivity isnt everything. I reckon your chip will be more than sensitive enough to pick up some good detail in the objects being imaged.

as far as filters go, the basic one are RGB (red green blue). You take an image, or series of images, through each filter and use software, perhaps includud in your DSI, to create a colour image.

The ones supplied by Meade may be perfectly good (I havent used them or seen a response curve), but other sets do exist, made with higher quality materials. Baader make LRGB sets for £80 I think, and they have a good reputation.

Perhaps i am going to far here for a newbie, but I think it is important to understand the physical processes going on in the various objects being imaged.

I hope this isnt patronising...

A spectrum is how a variable, like brightness or transmission, varies with wavelength, or colour of light.

Some objects have a continuous spectrum. That means they emit light over all wavelengths or colours. The best example of this is stars! Open clusters, globular clusters and galaxies, are all composed of stars, and so all these objects have continuous spectra.

Other objects have a discrete spectrum. This means that the only emit light at specific discrete colours. Nebula have this spectrum, both diffuse (north American), planetary nebula (Ring) and supernova remnants (Crab, Veil)

This does have important consequences for filters and imaging.

You mentioned that Hydrogen Alpha filters make for good nebula shots. Hydrogen alpha (Ha) is a prominent colour emitted by all nebula. It is the reason that most nebula when photographed appear red.

This filter is called a narrowband filter. This means it only transmits light around one specific wavelength. Ha has a wavelength of 656nm. The bandpass is small (typically around 10nm). These are different from RGB filters, as these filters have a wide bandpass (around 100nm).

Using a narrowband filter does no help when imaging continuous spectra objects like stars. All you do is constrict the amount of light passing to the camera, for no benefit. The only use a Ha filter would be is if you used it to record the star forming regions within a galaxy (M33), as these are composed of nebula, which emit Ha.

Narrowband filters do a good job of nebulae, because they have discrete (narrowband, if you like) spectra. These special filters only allow the light emitted by nebula to pass through, and block all others. Typical filters used are Ha, S[iI] (redder than Ha) and O[iII] (the blue colour of planetary nebula). Because they reject most of the light incident on the filter, they block light pollution (discrete spectra), and significantly cut out the moonlight (continuous spectra)

Where as RGB can be used for nebula (this is very common, as narrowband filters require longer exposures (10 mins or so)), narrowband shouldnt be used for contimuous spectra. For continuous spectra objects RGB does a great job, with shorter exposures (only a few minutes, but the more the merrier)

I thought I would explain the choices in filters as it pertains to the object you are imaging.

Ha looks great, but unless you image nebula it might be less useful just now. But Ha images can be incorporated in to RGB images for the best of both worlds.

I hope this helps explain whats what with filters and why they are used. You may already know this of course, if so, then sorry.

If there are any further questions, cameras filters etc, then dont hesistate.

This group will get you imaging faster than you can say hydrogen Alpha

Best Wishes

Paul

[mothershipuk]

Thanks Paul for that reply and no it wasnt patronising at all but very informative.

I have a whole stack of questions going through my mind at the moment and I am trying to find answers in the forum before asking in a post but that reply was fantastic and has increased my as yet very limited astro knowledge.

Cheers

Justin

[Psychobilly]

HI Mothershipuk,

Welcome to the forum and your first steps into astroimaging.

This is one forum where people dont seem to mind similar questions beign asked by different people "over and over" so as well as continuing your search through the archives just post your questions. Some of the older memebers may remeber what answers and advice have been given i the past and point you int he right direction.

I'm a relative newbie here myself and have only been at the game for about 16 months - this is by far the most useful "general" forum that I have found to date

Billy...

[narrowbandpaul]

justin,

like billy says...just ask away. It might be faster than trawling through previous threads.

There is a narrowband imaging thread that would give you more info on NBI (see Narrowband Imaging in the Imaging Discussion Page)

Paul

[Sam]

Sounds like you've got the bits and pieces to start having a go. There's nothing like learning through trial and error so I recommend you get some shots done and post them up - assuming we get clear skies of course. You'll soon find what are the capabilities of your system and what you prefer to image. Don't be worried about the qualitiy of the shots you post, there's lots of imagers just starting out so we can all learn this malarky together.

Sam

[mothershipuk]

Thanks again for the replies. Much food for thought.

Going to post my first imaging issue now and pray someone out there can help before I pull any more hair

Justin