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Deep sky, planetary, variable stars, asteroids, atmospheric optics, spectroscopy...
Deep sky, planetary, variable stars, asteroids, atmospheric optics, spectroscopy...
Astrophotography's posts

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Contact photography on photographic paper. Quick'n dirty test with excellent results.

About 1h30 exposure, cca 20cm from a 25W incandescent lightbulb. Took a photo of the negative and pulled on curves in Snapseed for about 1 minute or so.
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Pinhole camera version 1.0

85mm, f/170, pinhole diameter 0.5mm
Film : max 70mm height, cca 100mm width (180*)
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SETUP - Spectroscopy

We have available these days very high quality diffraction gratings (of the transmission kind) that can be used to split the light from a source and look at its spectrum.

I've played with this on a wide-angle lens, by sticking a 1000 groove diffraction grating on a regular UV filter - as can be seen below. I am now looking to do the same on my refractor, and look at stars. 

I can either stick it on the front of the refractor - and lose some light - or I can somehow adapt it in one of the clip-on filters that fit in the camera. First option is very feasible. 

So I come to you for advice, more precisely on the following:

Resolution for the first order - how do I calculate in angstroms / pixel the level of detail I would get for my CMOS sensor on the first order spectrum?

Distance between source and 1st order - will the star and its spectrum fit in my field of view? How do I calculate the angle at which the 1st order diverges from the optical axis? 

Maybe a kind soul with a knowledge of these number things may help?
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THE SUN - Sunspots 2443 & friends

A shot of yesterday's sun, showing spots on both the Eastern and Western limb. I've also added a comparative view of the Sun's apparent size at different focal lengths.

Really bad turbulence and only one shot.
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SETUP - How to align your Polar finder

Polar finders are very small refractors that give you true North with respect to Polaris. They work quite well, on the condition that they point precisely in the same direction as your RA axis - otherwise they're useless.

Most models have them embedded inside the mount, like the EQ 5, 6 etc. Smaller mounts, such as mine below, have it parallel to the RA axis, and at a certain distance from it. In both cases, it is essential that the polar finder be parallel to the RA axis.

Because of reasons linked to the distributor's idiocy (les blaireaux à Colmar), mine was in two pieces - the optics had been removed from the ring. So I had to put the finder in the ring - via 6 minuscule screws - and make sure it's pointing precisely where it should. 

The theory

Swing mount left and make it level - use LAT and AZ to center a faraway object in the finder.

Swing mount right and make it level - use the screws to make corrections on the finder.

Repeat until object remains centred in the polar finder when mount is swung about the RA axis.

In practice

- 6 screws so small they disappear instantly should they be dropped on the floor;
- they're positioned at 60° intervals, so at leat 3 are impossible to reach while looking through the finder
- a minute correction - maybe a quarter of a turn - shifts the optics so brutally that object disappears from FOV
- I realised that my wooden floor would bend if I pressed too hard when looking through the finder
- night was coming and I had 13° in the living room
- about 3 hours of torture the next day, and I somehow succeeded. 

A link on how to do it: 
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NEBULA - IC1805 Heart nebula

A random, 120s shot got me the below surprise. Framing is almost good.

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NEBULA - NGC281 Pacman nebula

The HII region is pictured here as it was 9500 years ago, when on earth Sahara was wet and fertile.

This is a single, 2minutes shot at ISO 1600. A satellite is visible as well.
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PLANET - Jupiter and satellites

One shot very early evening. The bands on Jupiter and the four largest satellites are visible.
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SETUP - lightweight

So I've downsized from 35kg+ to 15kg.

Takahashi Teegul Sky Patrol III tracking mount
Baader Stronghold alt/az tangent assembly
EQ5 to wide photo screw converter from Berlebach
Mini-tripod/pier Chinese mutant

This caries the 3kg 7D and FS-60.
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SETUP - portable mount

I currently use a small refractor and a 7D - the optics and sensor weigh less than 3kg. This is carried by a EQ6, which is a total overkill that is very bulky and particularly heavy.

I am very seriously thinking about getting the Takahashi Sky Patrol III or the Skywatcher star adventurer. I've read the specs and the first will carry 3kg for astrophoto, while the second is listed for 5kg. Knowing that I am quite tolerant about tracking errors - I really don't mind a bit of drift - do you guys think this is doable? also, the Takahashi is very small, but very pricey - 900 euros or so (about 750 dollars). The sky watcher is less than half, but considerably bulkier. 

Customer service is very bad where I live, and I have no opportunity to try either of them. Maybe one of you already used one and can give some advice?
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