I think any person who is interested in space has an idea to buy a telescope to see everything personally.

However, the harsh reality forever spoils all the raspberries: within the city - the whole sky is lit up with street lighting and the air turbulence is high. This means that you either have to limit yourself to the largest and brightest objects (like the Moon and Jupiter), or to carry a telescope far beyond the city.

A possible solution to the problem is remote-controlled telescopes of large size and located in the mountains. Of course, the ability to see everything with your own eyes will not replace it - but astrophotography obtained in this way will be hard to beat. It is on this method that I want to stay in this article.
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An example of what happened: the Andromeda Galaxy, M31 on the T20 telescope


When I had a desire to buy a telescope - I decided to recall the golden rule: before buying an expensive toy - it is always useful to rent it, perhaps the interest can be met with much less crap and costs. I searched for paid services for remote access to telescopes - and found iTelescope.net. There are also free ones - but there are very long queues there, and after all, give us everything here and now :–)

ITelescope has 19 remote-access telescopes installed at sites in Australia, Spain and the USA. All of them are located far from cities, in the mountains. The smallest telescope, where they let in general for free ( T3 ) - with a diameter of 150mm, taking into account its location, it already surpasses everything that can be seen in urban environments. Steeper telescopes - have a mirror diameter up to 70 centimeters with huge cooled digital matrices and a bunch of light filters (IR, RGB, narrowband for research).

The price of the issue - with a free account we are given 40 "points" and access to the simplest telescope, and for $ 5 (I paid with a mastercard yandex.deleg) - another +30 points and access to the "big" telescopes. Operating time on the largest available telescope costs 99 points per hour - only exposure time is considered. Those. if you shoot a galaxy, and take 3 pictures for 10 minutes (R + G + B) - then 50 points will be written off from you. Pictures of planets and other bright objects with a short exposure - will cost as a result 1 point on any telescope (less than 1 can not be spent). Thus, for these $ 5 you can take a couple of good pictures of galaxies / nebulae from deep space and / or a bunch of photos of the planets. Buying extra points will cost much more - about $ 1 for 1 point. But the initial 70 to meet the interest may well be enough.

Features of working with "large" telescopes:

Most telescopes have a huge (in area) cooled black and white matrix, and a wheel with light filters. This allows you to use unusual filters (for example narrowband) or shoot a black and white image to collect more light. Because color shots have to do in several exposures. You can make 1 brightness exposure more (Luminosity), and 3 less for color (RGB / RVB).

It is also necessary to pay attention to the type of matrix (indicated in the description of the telescope) - there are ABG (Anti-blooming gate) and NABG (not ABG). On NABG matrices with long exposures, bright stars will increase in area (in vertical lines), but they can be more useful for scientific purposes (since they are more linear). Also, NABG matrices have a slightly higher sensitivity. In my opinion, if we pursue aesthetic goals and need maximum image quality, it is better to use telescopes with an ABG matrix.

Telescopes are very unhurried - turning and focusing can go up to 5 minutes for 1 shot, so it may be difficult to remove the ISS :-)

Learn more about how to work with telescopes:

After login on the site you will be taken to the control panel:


There you can see free and busy telescopes. Clicking on the label "available" next to the desired telescope - you can log in to a specific telescope. Next, click on Run Image Series, in the Target Name write the name of the object that we photograph (for example, Jupiter, m33, m31, etc.) and click Get Coordinates. If there is an object in the database, there will be coordinates immediately. There is no moon in the base - in order to take a picture of it, you will need to know its exact coordinates at the time of the shooting. You can find them out at Stellarium (the necessary coordinates are there in the upper left corner of “RA / DE"). If you wish, you can also see the current screenshot of the control computer .



Then there is a list of pictures that need to be taken and their settings:

Filters:

R, G, B	Colored
V	Same as G
I	Infrared
Luminosity	Brightness (cut off IR and UV)
Clear	Transparent (decrease in clarity possible due to increased chromatic aberration)
Ha	H-alpha . Narrow-field filter of excited hydrogen line. Used to more clearly see details in galaxies and nebulae.
Oiii	Line double ionized oxygen . Allows you to see the details in diffuse and planetary nebulae.
Sii	Line of ionized sulfur . Lets see the details in the nebulae.

If there is enough black and white picture - it is better to shoot Luminosity or Clear - then the maximum light will be used. Otherwise - take 3-4 snapshots of RGB or LRGB. Duration - shooting time in seconds. For objects of deep space (galaxies, nebulae, etc.) - the more the better. The optimal results are 300–600 seconds.

The use of narrowband filters require an increase in exposure of 10-15 times.

Planets - require very short exposures; in 0.1–0.01 seconds + narrowband filters can be used (Ha, Sii, Oiii). From an economic point of view, using small telescopes (150–200 mm) with long exposures is unprofitable — it is easier to squeeze through a large telescope (500 mm) and take a brighter photo in less time. Last - all of these telescopes are generally sharpened by collecting the maximum amount of light, rather than high angular resolution. When comparing telescopes, it is necessary to pay attention to the “Resolution” parameter - how many angular seconds are in each pixel, what is the angular frame size (FOV) - whether what we want to photograph is placed there, or vice versa, whether the object is too small.

When choosing an object for shooting - look at the magnitude of the star. If this is a galaxy of the 15th magnitude, then even the steepest ground telescope will have a hard time. I would recommend starting with Messier’s catalog , choosing 7th magnitude and brighter objects there.

If the desired telescope is currently occupied - there you can create a shooting plan in the interface, and schedule shooting in automatic mode (no later than 4 hours before the appointed time).

Photo processing

Survey results are added to FTP (data.itelescope.net). By default, photos are saved in FIT format, with a 16-bit depth of brightness. FIT - contains not only the image itself, but also detailed information about shooting parameters. 2 versions are saved - directly from the matrix and Calibrated version. Calibrated - the main processing steps have already passed (subtraction of a dark frame, correction of different sensitivity of cells), it is usually easier to use it.

Next, the images will need to be converted from FIT to TIFF format using the FITS Liberator program:


Then - you can immediately into Photoshop, or glue individual RGB frames into a single color image (for this you need CCDStack or DeepSkyStacker). Links to these and other useful programs here .

You can combine several pictures in CCDStack like this: Open all the pictures, Stack–> Register, move the settings until all the frames match. Then Color–> Create, specify which picture is which color - and ready :–)

When processing the brightness of photographs of nebulae and galaxies with curves in the editor, I recommend trying something like the graph on the right (for each channel separately).

Conclusion and some of the resulting images:

I hope this prolonged post will either allow you to satisfy your cosmo – interest with a little blood, or understand that you really need your telescope :–)

I propose to share your best astrophotographs in the comments, if possible, upload archives with original files - in case someone succeeds in better processing.

Triangle Galaxy, M33 . 4 shots LGB + Ha, 5 + 3 + 3 + 15 minutes on T7.


Moon (0.1 sec with Ha filter on T16 - 150mm):


Jupiter Telescope T7 - ​​430mm. The satellites of Jupiter and even the shadow of Io on the planet are also visible.


By the way, regarding other planets - I looked at the distance charts to the planets in order to get the best photos, and the shortest distance from the earth to the planets is obtained in the following time:

Mars: closest 1st of April 2014. This is especially important for Mars - now there is nothing to see, the difference in distances is ~ 4 times.
Jupiter: 1st of January 2014
Saturn: 1st of July 2014 - Now he is on the side of the sun - and not catch him at night.
Uranus: Now
Neptune: 1st of August 2014
Pluto: 1st of June / July 2014 (Difference of distances - 5%, too far away)

Ps. The site tries to ensure that 1 person does not create several free / $ 5 accounts. We are of course all smart, but let's not abuse hospitality.