RBA Premium Astrophotography

Leo Triplet and NGC 3628 tidal tail

Posted: March 19th, 2009

Bigger size: 1776x1305

March 17,19,24 and 27, 2009

Exposure time:
L: 10x12' + 28x15'
RGB: 5x12' each
Total: 15 hours
Focal: 530mm, f/5 

Imaging scope: Takahashi FSQ 106 EDX
Camera: STL11000
Guiding camera: StarShoot Autoguider
Mount: Takahashi EM400

Henry Coe State Park and Dinosaur Point
Seeing: Ok
Transparency: Average to very good, depending on the date and time

Stacking: MaximDL
Processing: PixInsight & Photoshop


The Leo Triplet (also known as the M66 Group) is a small group of galaxies about 35 million light-years away in the constellation Leo. This galaxy group consists of the spiral galaxies M65, the M66, and the NGC 3628. Tidal and gravitational forces are acting between these galaxies, but even more interesting -at least to me- is the 300,000 light-years long tidal tail from NGC 3628.

You don't see often this tail in photographs. It is just so dim! As such, this image has been processed to show the tidal tail, but if the amount of light we see in this image coming from the tail as at that intensity, the light coming from the galaxies would be so strong that we wouldn't be able to see any details in the galaxies.

For this image, it was key to find a good balance between the quality of the sky and the length of the
exposures. I started taking 30 minutes subs, and I had to discard them because the sky glow would eat up
all the dim signal from the tail. That's why you see I used subs of 12 and 15 minutes. It turned out that both
worked well, unlike the 30 minutes subs, so I used both of those sets. In fact, afterfailing with the 30
minutes exposures, I tried 15 minutes and it worked well, soI settled for that, but one night the transparency
wasn't bad but not as good andI decided to go for 12 minutes that night.



Ann Sidbrant (Contact, Page), June 16th, 2009, 11:56
This is an amazing image. I have only seen the tail of NGC 3628 once before, and I look at quite a lot of astrophotos. It's not strange that the tail should be there - other interacting galaxies have tails, after all - but it must be exceedingly faint, since basically all other astrophotographers miss it. It sure adds some real drama to the dance of the Leo Triplet!

Me the color freak love the color difference you have managed to tease out of M66 and M65. Like the tail of NGC 3628, this striking color difference between the two well-known Leo galaxies is rarely seen. But it is so appropriate that it should be there, since M66 has a lot of star formation and M65 basically has none. In any case, the color difference between the Messier galaxies adds to the loveliness of the picture.

(By the way, I tried to post this comment earlier, but I couldn't because the "are you human" code I filled in wasn't accepted. I tried several versions of it, but none worked.)

RBA (Contact, Page), June 16th, 2009, 12:51
Ann, thanks for this and all your comments!!
Sorry about the "human" test, I guess sometimes it's a bit temperamental as well.
Yes, the tail is very faint - if you spend the time to get enough data, and process the image knowing it's there and "going for it", then it shows up ;-)

Javier (Contact, Page), October 14th, 2009, 2:03
Rogelio, la mejor foto que he visto del famoso triplete.....

Espectacular, ese talento lo echamos de menos en este lado del Atlantico..

See you in Spain!


RBA (Contact, Page), October 14th, 2009, 7:34
Gracias Javier!

Mat Drummen (Contact, Page), March 28th, 2013, 4:53
Dear Sir,

I'm preparing an article on the Leo-Triplet for the Dutch periodical Zenit, a non-commercial magazine for amateur astronomy in the Netherlands.
Can you give me permission to use your image of the Leo Triplet? Of course I will mention the author.

Thank you and best regards,

Mat Drummen

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