IC1396 - slap in the face

[rocketandroll]

DOH!!!

Ok, Olly, go on... say 'told you so' :-)

So... on the clearest night in years, with almost perfect visibility, and after playing about for an hour to try and get focus, I decided to 'tweak' it one last time before running a three hour session on IC1396 through the f2.8 L series Canon lens.

"You need to be really careful with the focus" I was told... did I check properly? NO!

Last time (hopefully) I make that mistake.

Anyway.... despite it being slightly (but noticably) out of focus... here is my new shot of IC1396.

This is a million times better than the last... I mean, you can make out it's a nebula for a start :-)

The elephant trunk is clearly visible... I'm happy with it... apart from the focus... about which I am trully gutted.

So... this is about an hour and 40 mins of 2 minute subs (longest I've tried unguided) at f3.2 and ISO 800 using the modded 350D with an LP clip filter.

I'm just off to drown my sorrows, or get some overdue sleep... or both...

Ben

[NickK]

Only thing is the focusing - the image looks like your next attempt is going to be a corker!

[Looking Up]

It's a great image even with the slight focus error, I guess it's just lacking a bit of definition, bahtinov mask no good for such fast f ratios?

[Peter Reader]

Amazing picture!

...how can you tell it's out of focus? :/

[ollypenrice]

I really recommend these things from Telescope Service;

They do one in a smaller diameter but it might just be too small for the EF200L. I wish I'd asked them but this does a great job. I use this and a FWHM measurement and a lot of patience (for which I am not famous in general!) because you have only a few microns in field depth before crossing the pixel threshold into blurredness...

But Hey, you have the big nebula looking mighty fine and even have some sky around it. When you think how big it is that's pretty darned good.

Olly

[rocketandroll]

I really recommend these things from Telescope Service;

They do one in a smaller diameter but it might just be too small for the EF200L. I wish I'd asked them but this does a great job. I use this and a FWHM measurement and a lot of patience (for which I am not famous in general!) because you have only a few microns in field depth before crossing the pixel threshold into blurredness...

But Hey, you have the big nebula looking mighty fine and even have some sky around it. When you think how big it is that's pretty darned good.

Olly

Cheers Olly...

Yeah, I recon I can build one of those for the 200L. I've got some 4mm walled 4" dia ali tube that should be about right for the rings.

Will try and get that done before the next attempt.

Ben

Sent from my GT-I9100 using Tapatalk

[Psychobilly]

On the newer canon cameras you can use Eos Utils to perform remote manual focus to use the computer to make tiny focus adjustments dont know if works with the 300D ... maybe only works on the liveview models...

I knocked up a set of the fine focus rings but know use remote focus instead...

Peter...

[ollypenrice]

Peter, with remote focus what are you actually looking at in order to focus? Do you have an FWHM to read or just an image of the star? Or something else?

Olly

[Psychobilly]

Using EOS utils - A Bahtinov pattern, or star shapes... you have three different step sizes in each direction... Works a treat with USM lenses as once you have focused you can swithc the lens to MF to "disconnect " the focus ring

In APT it works "automatically" using FWHM measurements

[ashworthacca]

I use APT's autofocus when imaging with my 70-200 lens. It gives FWHM scores so I put a bright star in the middle of the fov, put the lens in AF mode and run the autofocus routine. Switch back to manual focus and fine tune until I get the lowest score I can. Dont know whether or not this is the best way if doing things but it's very easy to use.....and works.!

[rocketandroll]

Cheers all...

Yeah, software focusing would be a help, but as this is my 100% laptop-free, 'drag it to anywhere' setup, I would rather KEEP it laptop free. If I'm gonna get a laptop then I'll go the whole hog and switch to dedicated CCD's anyway.

I'm gonna make up a set of micro-focuser rings for now, see if I can get it working better like that first.

One thing i did find... M5 was a great target for checking focus... I took about 20 frames of it, 30 seconds each, resolving out seperate stars was a good way to check focus. The key is not to then move the damn focus after it's perfect before you start a 3hr imaging run :-)

Ben

[Fay]

Well I think you did well with that Ben. We are all always not quite getting the focus right or not checking to see if it has changed. You will be fine next time, this is a great start.

Fay

[fatwoul]

I really recommend these things from Telescope Service

Since I apparently lack the skills to build these for myself, what are these jobbies called (on TS or elsewhere)? I was trying to search for one to show a friend at work, and came up blank.

[rocketandroll]

Since I apparently lack the skills to build these for myself, what are these jobbies called (on TS or elsewhere)? I was trying to search for one to show a friend at work, and came up blank.

...yeah, I had a job finding them too...

here you go:

Microfocuser and focus lock für camera lenses up to D=135mm

They come in three different diameters. For 50 Euro I may just buy one, it's a days engineering to make one tbh :-)

Ben

[Psychobilly]

it's a days engineering to make one tbh :-)

Ben

Unfortunately (or maybe fortunately) there are plenty of rainy days... and had the materials left over form knocking up couple of sets of scope rings...

Manual remote focus is a non starter for the non liveview cams...

For my older 350D I use DSLRfocus with Bahtinov's although it can also do FWHM...

For a computer free approach Bahtinov or Y mask and short(ish) high ISO exposures with careful review are about the only way of checking...

Nice target for the FL

Peter...

[fatwoul]

here you go:

Microfocuser and focus lock für camera lenses up to D=135mm

Cheers, Ben.

[rich_t]

With the lens mounted on a DSLR (rather than a astro CCD camera) is it possible to use the camera's autofocus system to focus on a bright star (I guess Vega would be good now) then switch the lens to manual so it doesn't move, then move to the target.

I'm pretty sure this worked for me in the past although it was a while ago!

Nice shot all the same, will be great with the focus nailed.

Cheers,

Rich.

[Psychobilly]

Rich,

I guess you would be relying on the CCD's senor and Cameras sensor being within a few microns of each other...

Peter...

[Moonshane]

On the newer canon cameras you can use Eos Utils to perform remote manual focus to use the computer to make tiny focus adjustments dont know if works with the 300D ... maybe only works on the liveview models...

I knocked up a set of the fine focus rings but know use remote focus instead...

Peter...

never seen one of these before - excellent tool. I can appreciate the benefits of this even as a visual only bod.

[rich_t]

Rich,

I guess you would be relying on the CCD's senor and Cameras sensor being within a few microns of each other...

Peter...

Hi Peter,

Sorry, I was meaning for DSLR imaging when there's no CCD camera, can you just autofocus on a bright star in the same way you would use the camera and lens for terrestrial daylight photos? Just move the lens to manual focus after to stop it shifting when you move away from the star?

Cheers,

Rich.

[Psychobilly]

Ah right yep that works or a bright planet and if the moons around you can use that...

[Multi-Coated]

Ben , it's all a bit over my head , but thanks for posting the image for us all to see , absolutely wonderful to the eye.