Mr niall

oh no its worse than I thought, it got so red that they changed it back to white...

I suppose the moral of the story is that I would kill for 3/4 skies 😉

52 minutes ago, Ships and Stars said:

Yep Glen Clova/Glen Doll/Glen Lethnot is wonderful. I've been camping there, no scope though, but it's on my list. A lot of people overlook the eastern glens for both tourism in general and astronomy. Away from Perth/Dundee there is a nice belt of darkness up in the glens running NE. 

At home it's a struggle, the business next to me keeps their rear light on 24/7. I made a cardboard and gaffer tape blinder that hang on their gutters, very lightweight, maybe 50g and doesn't touch the lights or get warm, and I remove it when I put the scope up for the night. Makes a big difference! No fuss, no mess😁 Tarfside would be a great spot, that's where the red pin is dropped at top centre of pic. I'm thinking about hosting a star party in NE Scotland within reasonable distance of Glasgow/Edinburgh this year. No one seems to host one up this way.

Wow, Bortle maps of where I live look like a badly sunburned goldfish...

amazing work, that's some serious dedication

Just an update - ended up buying a skywatcher mercury 607 (60/700) on an AZ2 with finder, 2x eyepieces and barlow that I found brand new on ebay for £48 , and an explore scientific white light filter for £18. So £66 spent so far...

Will report back.

On 14/08/2019 at 01:54, darkskyastronomy said:

July is good for Jupiter and Saturn, as well as all of the Messiers around Scorpius and Sagittarius.

It's warm, but the nights are short and not fully dark.

Yes but they’re so low it’s frustrating. I saw Jupiter through an 18” dob in the alps a couple of weeks ago it was like looking at a bowl of Angel Delight at the other end of the table 😜. After 5 minutes had just about made out 6 bands. No festoons. 

2 hours ago, vlaiv said:

 

I would rather go for 90mm of aperture and 900mm focal length than a smaller scope, but second hand one is OTA - which means you will need to mount it somehow. If you already have suitable mount - I think it is better option.

Main problem with such a cheap small refractor is going to be diagonal. Focuser is not going to be very good either (although usable) but there will be no difference between dob focuser and this one (in terms of quality). Diagonal is likely to be usable at best. Newtonians do have secondary mirror so no need for diagonal, and it is very likely that secondary is going to be of a better optical quality than cheap diagonal, so that is a plus for Newtonian.

There is option that will bring best views in WL and solve diagonal in the same go - but it is expensive. It is herschel wedge - special kind of diagonal that passes only small percent of light (around 5% and it is equipped with additional neutral density filter). It gives sharpest WL views, but can only be used on refractors (which is probably better choice with such small apertures). When using this herschel wedge you don't need baader solar filter - it does all filtering you need (just make sure ND filter is included with wedge).

But, like I've mentioned - it is fairly expensive piece of kit - it can cost more than scope it is being used on. I have this one and it is fairly good:

https://www.firstlightoptics.com/solar-filters/lunt-white-light-herschelsolar-wedge.html

You can couple it with polarizing filter, because light coming from the wedge is already polarized and additional polarization filter screwed on EP can be used to "tune" amount of light for comfortable viewing (and best contrast) - just rotate EP for desired light level before you tighten it in diagonal.

 

All good points sir, but I think we may be drifting away from the original aim which is to get up and running as cheap as physically possible. The way this conversation is going, I believe by the time this thread has run it’s natural course I’ll be purchasing a Quark to go on a Tak100 and mounting it all on an eq6... 😜

The 707 frac you showed me is very nearly twice the price of the mini dob - but from what you suggest I think it will provide double the experience so that’s ok. After that, well we’re getting into diminishing returns territory. If I enjoy it I’ll probably get a solar scout or PST as they look like a lot of fun but that’s some way down the road and I kind of just want something as cheap and straightforward as at all possible at this stage...

3 hours ago, vlaiv said:

https://www.firstlightoptics.com/evostar/sky-watcher-mercury-707-az-telescope.html

lovely looking scope - that might be just the ticket. 

Thanks all - I think that probably confirms the niggles I had about using a scope as a projector, I think I’ll probably steer my ideas back to the safety of either a filtered scope or a traditional projector.

now... small frac or small reflector 🤔🤔

53 minutes ago, Mark at Beaufort said:

The  projection method can be a simple setup, if you have a refractor, making sure you don't melt your eyepiece which I did.

49 minutes ago, vlaiv said:

Projection setup might be better for any sort of measurement and "precision" sketching - you put a tracer paper and then you draw "to template".

Thanks - as feared there appears to be lots to consider!

I will admit that projection would be a more appealing route if it offers a similar resolution to just viewing through baader film straight to the eyepiece.

but I must admit I am a little nervous about the whole “pointing a scope straight at the sun” nature of it. Is it not a little bit dangerous?  In my naivety and accident prone history I can’t help but feel that there’s a relatively high chance of me injuring myself or burning down the neighbourhood. I’ve accidentally started a fire with an uncapped 6x30 finder before and it was fairly frightening! And there’s kids and dogs at home that will no doubt “get involved”. Or have I misunderstood the projection concept?

Theres an evostar 90 Ota with diagonal and eyepieces on astroboot for £75 at the mo - do you think that’s more the sort of thing I should look at?

apologies again for the daft questions!

Hello there

I'm trying to create the worlds cheapest white light solar setup. I'd toyed with the idea of getting the astromedia solar projector which looks quite cute and seems to work looking at the reviews but then was wondering if there was any fundamental reason why the heritage 76mm with a baader film wouldn't work equally well?

https://www.firstlightoptics.com/all-telescopes/skywatcher-heritage-76-mini-dobsonian.html

Or am I missing something obvious as I cant see anyone has ever actually tried it. I'm aware the people have done it on the 114p virtuoso so I guess its feasible. I'd really like to get into tracking and sketching sunspots so I'm thinking a classic projection setup may be fun but not quite have the resolution I'd need for quality sketches?

Sorry if these are daft questions, solar really is a completely new area to me.

How longs a piece of string?? 😉

Depends primarily on the age and condition of the scope, particularly the quality of the mirror. The same goes for the eyepieces; none of them sound particularly premium although combined would make a fairly useful set.

Camera quite a good one though provided it has all its bits and bobs. Possibly worth as much as £75-80.

As for the rest... a good 10" dob can usually fetch around £225 if its in good condition. But depends on condition.

I'm not sure the combined price of the rest of the accessories would command a high price. You're usually looking at half to two thirds of retail for well looked after equipment. Not sure if that is much help. 

I bought the helios mistral WP6 10x50 ED from FLO for £125 a few weeks ago. I was dubious about the ED claims for that sort of money but was tracking circling buzzards and eagles across the Alps for the last three weeks and there was an unbelievable level of contrast and lack of CA against any background so I would guess its certainly achievable at that price point although I don't know how. I did notice a slight drop off from about 85-90% out but compared to something like the Pentax ZD ED 10x50 I didn't really experience a noticeable difference. 

I really don't understand the economics of binoculars!

great images well done

Hello all

Probably a daft question (stupid boy!) but I've been pondering the effects of ISO on DSLR imaging.

Due to my roaring ineptitude I limit myself to relatively short exposures with a wide lens (recently bought the canon nifty 50 based on recommendations here and what a lens!) but I'm aware that wide field exposure in suburban / rural areas is often limited less by accuracy of setup and more by the blowout caused by light pollution. The advice I have always received is to lower the ISO to compensate for this and therefore still obtain longer exposures.

And it is this I have been pondering. I understand how ISO works (at a rudimentary level probably) and obviously that in its most simplistic terms its analogous to increasing the sensitivity of the sensor at the expense of introducing noise. I quite liked the way that somebody explained to me once that it was similar to the "gain" control on a guitar amp; the way you can dial it right up but eventually it just becomes a distorted smush (mine goes up to 11!!).

My question is (sorry took a while to get there) is that does taking a longer exposure picture at a lower ISO provide a fundamentally better picture than a short exposure picture with a higher ISO? I'm not talking extremes here - I normally work in the 400-1600 ISO range and with exposures from 20 to about 120 seconds. But what I'm wondering is; when I'm getting LP blowout at say 90 seconds with 1600 ISO should I be:

• lowering the ISO to preserve the exposure length?
• lowering the exposure length to preserve the better level of sensitivity. afforded by higher ISO?

How would those changes fundamentally impact the image?

I don't dither or bin, I just stack and stretch, and I always take darks (but I rarely take flats as I just can't seem to get them to work at really short focal lengths).

Any insights appreciated.

Many thanks all!

Nope never heard of sky at night until long after I joined this forum. Patrick Moore was always the games master to me!

wow...

52 minutes ago, Ags said:

If you are going to shoot at F8, you may as well save the money and just use a kit lens.

Yes good point - but I was hoping to hit something in the f2.5 to f3 range which it looks like is easily achievable. My kit lens at 55mm is 5.6 I think, so yes trying to significantly improve on that as an attempt to mitigate my rather slap dash and incompetent attempts to polar align and track! 🤪

1 hour ago, happy-kat said:

I stop down more because of bright star bloat then corner sharpness.

Yeah… do you know that never occurred to me until I started this thread! I've always shot wide open and wondered why I'm getting such bloated stars with my 75-300. I always assumed it was either a focussing issue or a tracking issue (which it probably was as well) and I know the 75-300 isn't, objectively speaking, a brilliant lens that has its own issues; but this thread has really opened my eyes as to the importance of using a more conservative f stop. I love this place! 👍👍

The 120 is a cmos not a ccd but yes you're on the right lines.

DSLR and CCD imaging are fundamentally identical - but if I'm reading your post right I'm assuming you are taking ccd imaging to mean planetary imaging.

Planets are bright - so they don't need long exposures. But they're small so they're more sensitive to atmospheric wobble and fuzziness; just as when you look through the eyepiece and see planets change shape, colour, contrast, clarity and sort of wobble around. So, because they are small you don't need a large DSLR sensor as 99% of the sensor is looking at nothing, a smaller one is better. In the same way that a small eyepiece creates a more zoomed image, the same is true for camera sensors - so a smaller sensor is a double plus in that regard. Additionally one that is extremely sensitive is a plus. And that's fundamentally the difference between a DSLR and Planetary camera (not CCD - they can have sensors that are all the way up to full frame in size) a good planetary camera has a very small, very sensitive sensor. Resolution is largely irrelevant; as above - Jupiter at its biggest is only 49 arc seconds across so that's only going to take up a couple of hundred pixels at most; there's literally no point having a 24mp dslr sensor pointing at it as 99% of the pixels will see nothing.

The other reason that this is a plus is the fact that you don't actually photograph planets, you video them. Because of the wobbliness described above you have to take many many short exposures of a fraction of a second. Really at least 200, but as many as 5000 through a video recording. From that you review every single frame if possible, discard the poor ones and keep the good ones.

You have a choice of processing these through something like Autostakkert!2 or Registax (both free) and it stacks these all together as with traditional DSLR photography and voila! 

That is a very very short explanation but should give you the idea. There are lots of guides on google. 

(all that being said, you can take good planetary images on a DSLR, especially if it has a 1:1 crop on lower res videos (which few have these days sadly) but the main point here is that planetary imaging is a different discipline to long exposure short focal length astrophotography)

Hope that helps

edit: here is a pretty good guide that does a better job of explaining it than me http://www.star-hunter.ru/en/planetary-imaging/

Thanks all - following advice I've managed to picked up a new Canon EF 50mm (the newer STM version) for £89. I'll be quite honest and say the price was the deciding factor over the 40mm which does look lovely but at £89 that represents pretty brill value for money.

If I can get some half decent subs from this then the longer term plan is to pick up a Samyang 135mm but that is a significant jump in budget and focal length so the 50 will doubtless keep me going for a while!

Will report back with findings.

1 hour ago, Macavity said:

I did TRY to TEST a Pancake 24mm f/2.8 versus an EF 50mm STM f/1.8 😛
https://www.amazon.co.uk/Canon-EF-1-8-STM-Lens/dp/B00XKSBMQA
I used a Test Card on screen (not at infinity!) and scaled images to match...

The left hand image shows Centre performance of the lens.... the right hand image shows Edge performance!

Pancake 24 at f/2.8

The following suggests quantitatively the EF 50 STM has to be stopped down to f/4.0 (or more) to match the Pancake f/2.8 ????

EF 50 STM at f/1.8

EF 50 STM at f/2.8

EF 50 STM at f/4


ASIDE: The last image had some *camera shake* rather than astigmatism or whatever! lol 🤔

Does the above really MEAN anything? Who knows?!? lol! I TAKE it to mean that Canon lens
performance scales with price?!?!? The 40mm Pancake is said to be better than a 24mm too?

BUT throwing caution to the wind, I tried a 10x stack of 2min images at f/2.8 with EF STM 50!
I used dark subtraction,  IRIS Gradient removal and image enhancement with GIMP 

[removed word] Grana Salis as they say!

wow that is super useful - can see a massive difference between f1.8 and f2.8, that would probably be good enough for me (I'm nowhere near competent enough to approach the limits of equipment under even moderately normal use so can't see that being a limiting factor!)

1 hour ago, happy-kat said:

After reading a detailed review with images of same target across the f stop range between the nifty fifty and pancake I bought the 40mm pancake lens which also suits me for it's size.

You wouldn't happen to remember what the review was called would you (I must admit I'm a real sucker for pancake lenses. I used to have the M-fit pancake on my old eos M1. What a lens...)

36 minutes ago, toxic said:

the 50 is great - in daytime photography its as sharp as you will get but in astrophotography you need to sop down to F5.4-for nearly sharp to-F7.1 for realy sharp stars in the corners.

example single 120 sec at F7.1 canon 200D with 50mm on SA no processing just converted to jpeg for posting.

 

wow those are some sharp edges. Shame you have to go down to f7 though. Although I guess at £80 its not fair to complain.

Hello there

Can anyone recommend a good cheapish fixed lens with a standard Canon fit in the 50-100mm range? I've noticed there seems to be a fair few nifty fifties out there but I'm not seeing a huge amount of info on edge sharpness or distortion that seems to be the bane of my life with my otherwise excellent 18-55 kit lens. 

Ideally I'd like to be hitting around f3 or lower too if I can! 

Thanks all! 

This was touched on in a thread a couple of years ago may be of some help: