FinderCam Arrives (but still cloudy!)

[Macavity]

In the hope of finding a suitable (budget) "Finder Cam", I eventually bought one of these:

http://www.cameras-c...-pinhole-camera

Of all cameras of this ilk (with automatic AGC) this one seemed to have the best prospects?

Notably, a B&W 1/3" Sony ExView Chip with sensitivity of "0.003lux" - Albeit 400TVL only.

For just a shade over £60 (inc. next day special delivery) this is what you get in the box:

Cute (tiny!) cam in solid metal box. Lead that plugs in. (I added the chrome bit - See later!)

Comes with a (credible) datasheet, confirming that this is indeed the thing I expected!

After an initial play in the daylight, the camera looked promising - At least as a observatory

monitoring camera. This thing can (almost) "see in the dark"! With faint Red LEDs lights on,

in the observatory, it's as clear as daylight. So Boy, this thing is sensitive!

As you can see, I have now removed the conical pinhole lens. It unscrews easily enough, after

loosening the retaining grub screw. With a tiny bit of file work, a standard 1.25" e.p. nosepiece

fits flat / flush on the camera body (Made for the job!). I added a blob of epoxy at the corners.

With a (thoroughly light proof!) lens cap on, I get a "dark frame" like this:

At the moment there is some electric interfearence (not seen on the screen itself) - But you

get the general idea? The screen is *almost* black. I can see faint noise in the background.

Notable are a few HOT Pixels! Unfortunately Sony ExView Chips are rather prone to these?

The acid test is under the stars tho'. Since the above, cloudy grey skies for TWO nights!

Will it be swamped by sky background? Will it see any stars at all? I am relatively optimistic

But who knows? Sorry to tantalise! I do have everything set up for that moment's notice...

[shirva]

Allways fancied a board camera. ..for Peltier cooling mod.. Davy

[Macavity]

Wahey! A (2hr) gap in the CLOUDS last night!

For the purpose of this test, I used my trusty, battered, ST102 as a "finder".

As a first go, I zeroed in on a second magnitude star (Epsilon Pegasi or Enif!)

This is the image with the Exview Chip at prime focus (D=102mm, f=500mm):

So, the "finder" certainly sees magnitude TWO stars. This is encouraging!

And certainly much brighter than my new friend the (inevitable) HOT pixel!

Let's go for something a bit more challenging: Alpha Delphini or Sualocin...

Hurrah! - It can see 4th Mag stars! And, as an added bonus, a 6th Mag Star!

In comparison, this is the field delivered by Watec 120N+ with NO integration:

As expected, the Exview Chip is slightly more sensitive than the Watec Chip.

But (thankfully!) the Watec image is cleaner, has a larger image scale etc.

What of DSOs? (Remember this is FINDER Camera!) Here's the M15 Field -

Conveniently it has a surrounding triangle of fainter stars (c.f. S.J.O'Meara):

I might even claim that you can JUST about see M15 with the Exview chip!

Should I throw away my £600 Watec and replace it with a £60 Cam.

Clearly NOT! The Watec has the possibility of hardware integration:

Conclusion: Small "Exview" cameras have real possibilities as a "Finder Cam"!

From the above experiment with 100mm F5 scope, subtract one magnitude for

a 60mm finder (1.5 mags for 50mm finder). But ADD a bit for faster f-numbers?

P.S if you have a really LARGE Dobsonian (plus small LCD screen) thse things

might be handy in avoiding ladders? Even those among us with modest Newts

aren't always as agile as Olga Korbut (Ask your Dad?) these days!

[JamesF]

Do you think the additional noise on the Exview camera is random, or would it perhaps submit to dark frame subtraction?

James

[Macavity]

Dunno, James - Not really advocating it as an imaging camera? Most of the grey background seems to be random noise? I suspect the HOT pixels can be reduced by subtraction of dark frames. "Flats" might remove the frequent (thermal) electronic noise gradients too? These small cameras do get quite hot! - . And the noise increases perceptibly. Maybe Davy has the right idea re. Peltier Cooling or something?

Some brave souls have even modified these cameras for long exposure etc. etc.

http://jaggedplanet.com/ExViewMod.html

This Cam has the SAME chipset. But I KNOW my soldering skills ain't equal to such things!

Exview Chips seems to be an impressive Sony experiment that never quite achieved commercial viability?

If you are an Astronomer, might be useful to buy up the remaining (useful!) stocks though...

[JamesF]

I was thinking that dark frame subtraction might improve the video image quality too. Just as it's used in PHD, for example.

James

[shirva]

Cracking write up Chris ...Davy

[Macavity]

Thanks, Davy! Now, if only I could afford half a dozen of them for various (rather pointless) tasks.

An excuse maybe, but I do think the "headlight through fog" appearance of brighter stars might be in part due to high cloud last night? My ST102 presumably delivers a lot of "purple haze", and now near infrared to defocus the image too? It's a shame the "security" industry doesn't quite have the (Exview) needs of Astronomers in mind.

[Carl Reade]

Hi, Chris interesting stuff, have you concidered a focal reducer to try with it?

[shirva]

Lol...if they did that Chris they would stick another hundred quid on it...the st102 is a nice scope and good for visual but dosent half have ca on the ap..that's why I got the ed80. ..Davy

[DIYASTRO]

Chris,

Good report!

I have been trying out the Sony 1/3" Super HAD CCDII. Its part of the Sony effio range CDF70 series. The advantage over the one you are trying is that they are 700TV lines and still 0.001 lux. I am going to try it in my finder which is part of my astro camera set up which I posted in the DIY section. I have built in a cooling fan which helps with the progressive heat build up but may cool via peltier.

Keep us informed as to progress, very interesting!

Boyd

[Macavity]

Thanks for the enthusiasm(!), guys. A clear night last night, but not a LOT to add? Instead of my (trusty) ST102, took a few pictures with my TS "Super Finder" (D=63mm / f=228mm - F = 3.6!)

http://www.teleskop-...al-focuser.html

The "image scale" changed, clearly(!), but not a lot else? Hot Pixels still appeared as Mag +7 "stars". I could detect Mag +9.5 stars even! But Mag +4 stars were still the "bread and butter" for *finding* stuff... SYNCHING EqMod GoTos etc.

I did put the (popular!) Atik 0.5x focal reducer on the end of the (tacked on) Camera nosepiece. I was limited by in-focus, but maybe simulated a typical 50mm (f=6") finder? Again not much change! I even tried a Baader UV / IR cut filter, but not a lot of difference. Mag +4 stars were still emminently accessible! I declare this Camera reasonably OK for it's projected function. LOL.

DIYASTRO - Love the pictures... And the ideas! I have a "tame machinist" but not your skills! I'm sure a bigger "TVL" would improve things. Unfortunate these advertiser "specs" are so arbitrary?