Eyepieces.. :(

[AweSIM]

@jahmanson.. thanks dude.. so its basically for people who KNOW their way around the sky and dont need relying on fancy GOTO mounts like myself to tell them where andromeda is.. .. but one thing still bugs me.. why arent a lot of people interested in photography? to me it seems like a natural step forward.. ive learnt here that no matter how big a scope you have.. photography will always beat visual observation since you can not do long exposures with your eye.. whats keeping you guys from delving into astrophotography? budget? spouses? .. no offense to anyone.. ..

[John]

Astronomy is a broad hobby - everyone can participate in in just the way they want. For me it's always been about visual observing and I've never felt the urge to image but I really admire those who do. I don't in any way feel "inadequate" about that of course and there is no need for it to "bug" you either

For me, I want to see these objects with my eyes even if they are faint and hard to discern - thats all part of the fun of it

On your earlier question on the field of view of a 40mm 1.25" eyepiece v's that of a 28mm 2", the 1.25" barrel restricts the apparent field of view to 43 degrees wheras the 2" eyepiece can have 70 or 80 degrees (my Nagler 31mm has an 82 degree apparent field of view). So it's perfectly possible to have a more powerful 2" eyepiece showing more sky than a less powerful 1.25" one.

[AweSIM]

i agree with you.. i assure you i didnt mean any offense.. it was just curiosity.. .. as for the EPs.. so 2" EPs ARE better than 1.25" ones.. that explains their higher costs.. thank you for clarifying that out..

correct me if im wrong.. what i understood from you and some physics is this.. 1.25" EPs have tighter stops than 2" ones.. so for the same focal lengths.. the 1.25" will have a lesser FOW than 2".. and low mag EPs will suffer from vigenetting if they are 1.25".. so.. if i wanna go for high mags for planetary observation.. i can work with 1.25" ones since even though theyd have an apparent FOW of 40 degrees.. the magnification will lower their actual FOW to lets say maybe 10 degrees.. but for low mags for wide field work.. it would be a waste to opt for 50mm 1.25" EP since its FOW would not allow it.. and the image youll see in it would look either..

- vigenetted or..

- a larger black circle around the FOW..

am i correct in this interpretation?

[AweSIM]

addendum.. does anyone know model numbers of SkyWatcher moon and sun filters for 200P? im purchasing from Telescop Express and i cant find one that fits this scope.. i was thinking of settling for Orion Solar Filter OR7744.. []Orion Sonnenfilter visuell - optisches Glas - Aufsteck D = 216mm..

this has a diameter of 216mm which is larger than 200P but it has screws which i think i can tighten around the scope aperture..

[Orion_the_Hunter]

As an eyepieces focal length increases, so does the FOV, until it reaches a point where the FOV is as wide as it can be through a 1.25inch ep.

(I know what I mean, Jameson will be able to explain better than I have done).

Whilst it is better to get decent quality eyepieces, you don't necessarily need to buy Tele vue or Hyperions, there are plenty inbetween that price range and your budget.

It really depends on what you think you can stretch to per ep.

I am also interested in DSOs therefore I recently bought a 32mm 2" First Light Optics - Skywatcher PanaView 2" eyepieces for about £80. It was pushing my budget but has been well worth it. It meant that I couldn't buy another ep for a while. So now I'm saving for a 14mm First Light Optics - Meade Series 5000 Super Plossl

(I think).

HTH

Ed

[Orion_the_Hunter]

one thing thats been constantly bugging me.. would someone PLEASE make me understand.. why are DOBs so popular?

.. but is the cost factor the only factor people look for in these systems? or have i missed something?

They are very easy to set up & use and are very sturdy.

Because of disability I had to choose my scope really carefully. I eventually settled for a Dob because of the viewing position but mainly because it's so easy to just 'point & look'. I'm glad I did because that simplicity is what I love about it.

If I had an EQ mount I would have thrown it off the balcony by now, that's just me.

[AweSIM]

@orion_the_hunter.. no brother.. you explained it beautifully.. you and jahmanson TOTALLY cleared it.. .. thank you.. both of you.. ..

addendum.. i just finished searching Telescop Express site.. and here's the list of items ive compiled.. FINALLY.. thanks to all of you people whove helped me reach this point.. i know its a huge budget.. but im going to bring it over in batches.. check this list out and criticize me on it.. things i might leave out.. things i might replace with other things.. things i should get at all costs.. ..

--[ This month ]--

- SkyWatcher Explorer 200PDS - 345 EUR

- Orion Solar Filter - 139 EUR

- Skywatcher Adapter from M48 to NIKON Bajonet - 20 EUR

- Tele Vue 2x Barlow 1.25" - 96 EUR

- Tele Vue Plössl 15mm 1.25" - 78 EUR

- Cheshire 1.25" collimation eyepiece - 20 EUR

= 700 EUR

--[ Within Next Two Months ]--

- Skywatcher NEQ6 SkyScan Pro - 1049 EUR

- Orion Anti-Vibration Pads - 64 EUR

- Orion Illuminated Crosshair Eyepiece - 69 EUR

- TS Filterset 1.25" with 5 filters - 49 EUR

= 1250 EUR

--[ Later ]--

- more EPs according to my needs and you guys' advice..

- more filters according to my needs and you guys' advice..

ps.. the list items are linked to the website.. you can click to see the full specs.. ..

i know i wont be able to use the scope till i have the mount too.. but im doing this cuz i have a friend coming over and i want to have the scope hand-carried.. the mount can be shipped later.. just have a look at this kit and share your opinions regarding it.. is it sufficient for a couple of years? is it too luxurious? is it redundant? hit me!.. ..

once again.. thank you all so very much.. without your help.. i would never have been able to reach a point of decision so quickly..

asim sohail..

[AweSIM]

@orion_the_hunter.. i understand your point of view brother.. .. although i dont feel comfortable with dobs.. i dont know why.. maybe cuz im a novice.. .. and have a LOOOOOONG way to go..

[david o]

Hi Asim,

Before you jump into buying anything for astro-photography you'll find the book Making Every Photon Count (by SGL's very own steppenwolf, now into it's 2nd Edition) essential and helpful in getting started.

Easy to read, it's full of advice aimed at the imaging novice, including tips 'n' tricks, lots of other vital stuff and, most importantly, choosing the right equipment. Helping you avoid costly mistakes with kit you won't need or use.

Have a trawl through the imaging sections too, They're full of info and some very experienced, talented folk who, I'm sure, will be more than happy to share advice and guidance with you.

[AweSIM]

david o.. i like the sound of that.. the window of opportunity for me is very small.. its once every two or three years that a relative comes back from abroad with whom i can have the scope brought.. so i have to order the OTA at the very least.. i think the following plan can fit together nicely too..

- get OTA and the book this month.. keep the OTA in the vault and start reading the book..

- get mount the next month.. fix the OTA on it and start basic observations and continue reading the book..

- get all the filters, gadgets, EPs the month after that.. ..

but as far as the items in the kit are concerned.. what do you think of the setup detailed in my last post? is it good? extravagant? deficient in some aspects or what? the thing to keep in mind is that unlike you folks in europe.. i dont have an easy access to equipment here.. neither can i sell it off to upgrade etc.. you guys are lucky.. .. ..

-

[david o]

I'd also advise reducing your shopping list to something like this :

--[ This month ]--

- SkyWatcher Explorer 200PDS - 345 EUR

- Cheshire 1.25" collimation eyepiece - 20 EUR

- Baader 2" 12.5% transmission neutral density filter - 38 EUR

- Baader 2" Skyglow Neodymium LP filter - 72 EUR

- Televue 11mm Plössl - 78 EUR

= 553 EUR

Get a 2 inch filter, it can be used with both 2" and 1.25" EPs - the 2" to 1.25" adaptor that comes with the 'scopes focuser should have 2" filter threads.

--[ Within Next Two Months ]--

- Skywatcher NEQ6 SkyScan Pro - 1049 EUR

- Orion Anti-Vibration Pads - 64 EUR

= 1113 EUR

You'll have a steep enough learning curve with just this "simple" 'scope and mount set-up. Only add complexity, in the form of more kit / beginning imaging, when you've mastered the basics.

--[ Later ]--

- more EPs according to my needs and you guys' advice..

- more filters according to my needs and you guys' advice..

Edit

You posted as I wrote this. Seems that we've come to think alike

[AweSIM]

hehehe.. i guess im learning too.. .. .. im gonna stick to your list now.. seems more decent.. three questions though.. as usual.. ..

1. why opt for a 12.5% filter? isnt it better to go for a variable polarization filter? just curious..

2. the filters you chose are 2".. the TeleVue EP is 1.25".. will it work with it too or only the stock 2" EP? i just cant understand the whole 1.25" fits 2" and vice versa idea.. im trying to find out if theres an image of the section of the focuser so i can understand how in the world it actually fits..

3. and lastly.. what made you go for 11mm instead of the 15mm that i had chosen? the previous setup gave 36x and 67x without 2x barlow.. your recommendation gives 36x and 91x.. isnt that two extremes of magnification? obviously you know more than i.. i just wanna understand how did you decide upon this?

[david o]

Only three ??

1. I was thinking that no moving parts = less to go wrong = more robust and durable, but the polarization filter does allow you to adjust things to your needs.

2. Imagine the focuser, a tube wide enough to take the barrel of a 2" EP with set screws or a compression ring to hold it in place.

Now imagine that instead of a 2" EP you place an adaptor in the focuser tube. It's a very thick walled tube with an internal diameter just big enough to take he barrel of a 1.25" EP, again with set screws/compression ring to hold it in place.

The bottom of the adaptor, the opposite end from the EP, is threaded to accept 2" filters. Allowing you to use 1.25" EPs with 2" filters, rather than having to buy both sizes of filter.

3. I went for the 11mm to give you a medium/high power EP rather than the medium(ish) power thaat 15mm would give:

* 11mm Plössl, giving ~91x (= 5.5mm Barlowed, giving ~182x)

* 15mm Plössl, giving ~67x (= 7.5mm Barlowed, giving ~133x)

Also the included 28mm EP, when Barlowed, will give a magnification very similar to the 15mm :

* 28mm LET giving ~36x (= 14mm Barlowed, giving ~71x)

Why overlap, when your money can give you a better spread of magnifications ? 36x, 71x, 91x & 182x as opposed to 36x, 67x, 71x & 133x.

If you do get a Barlow, get a good quality 2" one. Just like the 2" focuser it will have an adaptor for 1.25" EPs - one Barlow working with both EP sizes.

HTH

[BinocularSky]

o why are DOBs so popular?

Simple, very stable, inexpensive altazimuth mount, held together by gravity and amenable to being home-made, means that more of the resources can be put into gathering light. It is capable of being upgraded either by placing it on an equatorial platform or by "Bartelizing" it.

You are correct that they are not suitable for imaging

Hmmm. Common misapprehension, that. Whilst it is partly true of a Dob in it's "native" state, counter-examples to the general assertion:

• Jack Martin does many of his excellent spectrograms with an undriven Dob, using the drift to broaden the spectra. See here (and scroll both ways for more examples).
  
• Tracking can be simulated in software by stacking multiple short exposures.
  
• It is relatively simple to motorise a Dob and incorporate field derotation... or pop the Dob on a Poncet or other equatorial platform.
  

See:

Dobsonian Astrophotography

Terrastro Deep Space Hi-res

Robs Astro-Photography

Astrophotography

(and many, many other examples on the 'net)

[John]

....Hmmm. Common misapprehension, that. Whilst it is partially true of a Dob in it's "native" state, counter-examples to the general assertion:

• Jack Martin does many of his excellent spectrograms with an undriven Dob, using the drift to broaden the spectra. See here (and scroll both ways for more examples).
  
• Tracking can be simulated in software by stacking multiple short exposures.
  
• It is relatively simple to motorise a Dob and incorporate field derotation... or pop the Dob on a Poncet or other equatorial platform.
  

See:

Dobsonian Astrophotography

Terrastro Deep Space Hi-res

Robs Astro-Photography

Astrophotography

(and many, many other examples on the 'net)

You are quite right Steve - I was tired so I gave a generalised reply

I've done some basic planetary imaging with dobsonians myself.

[Vicky]

I've chosen a dob because I want to enjoy seeing more of the stuff I'm learning about in the two OU courses I'm currently studying. I'd love to image too but the time and energy that it requires is more than I wish to commit right now- at least with an 8" dob I can upgrade to a EQ mount and motor at a later date, should I end up wanting to go into the photography side.

Its funny, I started off my search with 'no dobs' as the only thing I knew for sure, and weeks later thats precisely what I've ordered.

For me the compromise between getting a smaller telescope that can image (with lots of twiddling and electrics etc.) vs the simplicity (easy set up) and bigger mirror made the dob a no-brainer for me. I know its not everyones cup of tea, but I want to start simple and get to know the sky around me first. And yes, I get a bigger scope for less money, which always has a habit of coming into the equation!

Happy shopping!!- all those goodies- I'm getting a moon filter but suspect a Barlow and or solar filter may not be too far behind...

[AweSIM]

@david o.. hehe.. yea.. three for NOW.. .. anyways in response to your clarifications..

1. i understand.. so its basically up to me if i wanna go for a variable polarization filter or not.. but the fixed ones are more durable since they have no moving parts..

2. brother you explained it beautifully.. so much that i even could visualize the focuser assembly.. ive even made a graphic of it.. lemme know if i understood it correctly.. ..

3. i get it now.. i was missing the point you made.. i was opting for a 1.25" barlow.. so it meant that the stock 28mm could not be barlowed.. since i didnt understand the concept of interchanging 1.25" and 2" EPs.. but thanks to you.. now i do.. and youre right..

- barlow 2x 2"..

- 28mm 2" stock EP..

- 11mm 1.25" Plossl EP..

- 2" filters depending on cash reserves and amount of drooling.. ..

thank you so much for that extremely useful post.. ..

@tetenterre.. hmm.. youre right too.. if you have a DOB on equatorial then great.. but i always stayed away from alt-azimuth mounts like meade or celestron catadioptrics since i learnt that their images suffered from field rotation.. true.. you could have a motorized assembly that rotates the camera or something to cancel the effects of field rotation.. but in my opinion.. equatorial mounts are better than alt-azimuth if you plan to do astrophotography.. there was a time when i used to drool for meade lx200 scopes with their awesome finishes and goto mounts and compact design.. but now i rather keep my distance due to field rotation problems.. no doubt these are great scopes for visual use.. compact and good looking.. but for astrophotography? maybe not..

image stacking.. hmmm.. i almost forgot about that.. yes ive heard about celestron webcams that automatically perform image stacking and field derotation algorithms.. but my judgement tells me that an equatorial mount with long exposure should still fare better than an alt-azimuth mount with image stacking and derotation.. my logic for this is as follows..

to expose a silver crystal on film or trigger a pixel on a dslr sensor.. a number of photons would be required.. if the mount is alt-azimuth.. the field will rotate and photons from a single star will not hit a single pixel and trigger it.. rather it will smear an arc of pixels.. like star trails.. t reduce the trails you can try reducing the exposure time for each image in the image stack.. like maybe 1 second exposures.. but that could lead to so low photons per image that the sensor doesnt trigger.. so youd have to still expose for 30 seconds or so and even 30s image do show star trailing.. ive seen that myself while shooting with dslr only.. so if you have an alt-azimuth mount.. even if you employ field derotation and image stacking.. stars will still trail.. i hope i explained it well.. at least thats what my knowledge of physics tells me.. i may well be wrong in practical sense..

asim sohail..

[AweSIM]

@tetenterre.. my friend the links you posted regarding DOB astrophotography are really great.. crisp pin-point images.. really great.. i do respect DOBs greatly.. all the ppl getting DOBs and being happy with them cant all be dumb.. its most probably me whos the dumb one here.. .. but i believe that its not in my grasp right now.. maybe partly cuz we have no suppliers and dealers and resources here in pakistan.. the scope you get you get to keep it for a very lng time.. no upgrades.. no nothing.. ..

[david o]

Hi Asim,

That graphic really captures what I tried to explain

Nice one !

[AweSIM]

thanks.. you explained it well in the first place..

[david o]

Hi again Asim

Just had a thought on the theme of Dobs.

Almost everyone on SGL that gets one comments on how easy and intuitive they are to use - it seems to become second nature in moments.

You could always have the best of both worlds ! Thus :

--[ This month ]--

- Buy a GSO 8" f/6 Dob, not the Explorer 200P DS Optical Tube Assembly, and so be able to do visual astronomy straight away.

--[ Within Next Two Months ]--

- Buy the EQ6, as planned, but with a set of tube rings and a dovetail plate to mount the Dob's OTA

Whilst the GSO Dob does come with a dual speed Crayford focuser there are some downsides. With its 1200mm focal length and f/6 focal ratio it isn't as suitable for imaging as the 200P DS at 1000mm & f/5.

Also at 449 EUR it's over one hundred €uros more expensive than the 200P DS too ! Not forgeting to add the cost of the tube rings and dovetail.

It is just an idea though. I prefer my Eq mount over my Alt/Az too

[AweSIM]

hi david.. thanks for the idea.. ill look into it.. it seems tempting too.. in my opinion.. the f6 isnt a huge disadvantage.. i mean f5 vs f6? shouldnt be a huge difference.. but since i dont own ANY scope right now, let alone one of each of these two.. i cant compare them.. the price tag might be a problem though.. as is with everyone who wants to buy a top class kit they can possibly dream of.. ..

the main issue with me is cash at this moment.. the first batch of shopping is supposed to get me the OTA plus as many EPs, filters, etc that i can get.. cuz the second batch is already too expensive.. thanks to NEQ6.. .. so im trying to take as much weight off the second batch and stretch my budget in this first batch.. but if the OTA is more expensive and needs tube rings and dovetail bars too.. it stretches my budget for both batches..

but thanks for the idea.. you never know what you may decide next.. i started off with wanting to get meade lx200.. then celestron something.. then meade etx.. then astromaster 130 eq md.. then explorer 150 eq3.. and now explorer 200 neq6.. .. and if it wasnt for you guys.. i most probably wouldve ended up buying etx with the small eq tripod legs for DSO imaging.. wow.. i was dreaming about that scope two months ago.. now im laughing at it.. .. no offense to the scope though.. good started scope.. but wont last me ten years with no chance of upgrades..

[david o]

Hi Asim,

Dreaming up ideal, "perfect set-ups" of kit is an occupational hazard of star-gazing

If budget is tight then this probably gives the "best" value for money, with some future proofing too, for where you want to go :

--[ This month ]--

- SkyWatcher Explorer 200PDS - 345 EUR

- Cheshire 1.25" collimation eyepiece - 20 EUR

- Baader 2" 12.5% transmission neutral density filter - 38 EUR

- Baader 2" Skyglow Neodymium LP filter - 72 EUR

- Televue 11mm Plössl - 78 EUR

= 553 EUR

--[ Within Next Two Months ]--

- Skywatcher NEQ6 SkyScan Pro - 1049 EUR

= 1049 EUR

The Anti-Vibration Pads can safely be left for later, they are more luxury than necessity. But that's not to say that they aren't useful.

If you need to trim the budget even more then the Baader Neodymium can wait for later too.

--[ Later ]--

- more EPs according to my needs and you guys' advice..

- more filters according to my needs and you guys' advice..

Of course, if you just wanted to do visual observing... well, then a Dob with OEM Eps and a moon filter would give you the best VFM

[AweSIM]

@david.. thanks for the refinement.. i think this layout of batches of shopping suits me better.. need to decide on DOB though.. lets see about that.. a couple of things bother me..

1. why does moon filter have a higher priority than LP filter?

2. shouldnt i have a solar filter on the list too?

[david o]

No probs Asim

1.

Think how bright Luna can seem to the naked eye. Now multiply that by the extra light gathering power of the 'scope...

the glare can feel painful.

Then on the other hand LPR filters don't seem to suit, or work equally well for everyone - they're not a silver bullet.

Use your 'scope first and see how you get on with your local LP. If it really is an issue, then is the time to start thinking of getting one matched to your conditions - some are "stronger" (or "harsher") than others.

2.

How much priority to put on a solar filter really depends on how strong an interest solar observing has for you.

I may have been showing a bit of bias . It's not something that calls out to me, if/when it does I think that I'd be tempted to go for dedicated solar 'scope(s).