NGC 4088 – Galaxy In Ursa Major: May Observer’s Challenge Report #172

Mario Motta: Observer from Massachusetts

I finally had a clear night, as the weather has not be good in Massachusetts.

Cruel joke by God, placed the best galaxies in the spring, and the worst weather in the spring. NGC 4088, a galaxy about 51 MLY away, may be a barred spiral tilted to our line of sight.

It took two nights to collect the subs due to intermittent clouds.

I used RGB (1.5 hours), and LUM filters 75 minutes), then added Ha (30 minutes) as well for Ha nebulae regions. All taken with my 32-inch f/6.5 telescope from Gloucester MA, and with ZWO-ASI 6200 camera.

Processed in Pixinsight.

Roger Ivester: Observer from North Carolina

NGC 4088 was much easier than galaxy NGC 3044, which was the April challenge object.  However, NGC 4088 is still “extremely” faint. It has low surface brightness, highly diffuse and elongated. I could see this galaxy, but with difficulty despite a 4.8 NELM. 

Since I was using my GoTo mount, for this galaxy which made it much easier.  I used a three star alignment, rather than my normal two, which improves the pointing accuracy, and put the galaxy in the center of my FOV.  I’ve found it much easier if I know an extremely faint deep-sky object is in the center of the field. 

It was a cold night (March 14, 2023) and breezy, but with very low humidity. Years ago, this night might allowed me to see the galaxy much better and easier, but light pollution has increased in my suburban back yard over the past 40 years.

However, my observations prove, that even very faint galaxies can be successfully observed from a moderately light polluted city back yard. And it’s been years since I took a telescope to a dark site.

I really like the convenience of observing from my back yard for obvious reasons. It’s difficult for me to load a solid tube, very heavy 10-inch equatorially mounted telescope and with all supporting equipment, and driving to a dark site.

Yes, I have smaller telescopes, but the process of loading and unloading any telescope and equipment and driving 30 or more minutes to, and back from the South Mountains is still very time consuming and labor intensive.

Mark Helton: Observer from Massachusetts

NGC 4088, galaxy in Ursa Major 

Imaged from Ipswich, MA with a bortle 4/5

50 180 sec images at gain 100 -10 cooling bin 1×1
20 dark frames
25 flat frames
30 bias frames

Camera: ZWO533MCPRO no filter
Mount: Ioptron HEM44EC
Telescope: Celestron C-8 with .63 FF 1450mm f/7.1
Processed in Pixinsight and Photoshop

Really enjoyed imaging this target and the region around it.  There are a lot of points in this image that are much further away than these galaxies!

Larry McHenry: Observer from Pittsburgh

The 44° inclined spiral galaxy NGC4088 is located in the constellation of Ursa Major – “The Great Bear”, about 3.4° from the bright Big Dipper bowel star +2.5 mag Gamma Ursa Major (Phad).

This bright, deep-sky galaxy is about 51.5 million light-years distant, with a diameter of about 65,000 ly. 

It is considered to form a physical pair with nearby spiral galaxy NGC 4085, and are both members of the M109 galaxy cluster. NGC 4088 is also cataloged as peculiar galaxy Arp 18, (Spiral with detached segments), and displays a number of prominent knots in its spiral arms.

NGC 4088 (H1 206) was discovered on the night of March 9th, 1788 by William Herschel using his 20 ft reflector, from his home at Slough near Windsor Castle. (NGC 4085 was discovered a year later on April 12th, 1789).


Left-hand video-observation: 06/04/2013, from the Cherry Springs Star Party at Cherry Springs State Park, PA, using a 6-inch RC optical tube @ f/5 on a GEM mount, with a CCD analog B/W camera and IR filter, 20-second single unguided exposure. (North is up in the cropped image) NGC 4088 is above center, while the much smaller and more highly inclined spiral galaxy NGC 4085 is below center.

Right-hand video-observation: 05/30/2022, from the Cherry Springs Star Party at Cherry Springs State Park, PA, using an 8-inch SCT optical tube @ f/6.3 on a GEM mount, with a CMOS color camera and broadband filter, 180-second guided exposure, live-stacked for 30 minutes. (North is up in cropped image) Dwarf spiral galaxy MCG 92092 in lower left corner.

Using EAA techniques: The odd-shaped inclined spiral stands out well from the star field. What appears to be a stubby, detached spiral arm with a bright H-II knot extends to the NW. A number of other bright H-II regions can be found in the tight arms to both the north and south of the oval core of the galaxy.  

Phil Orbanes: Observer from Massachusetts

This unusual spiral is found in Ursa Major and is among the 50 or so galaxies of the M109 group.

One of its arms appears disconnected when viewed through large telescopes, and for this reason has earned a place in Alton Arp’s Atlas of Peculiar Galaxies. NGC 4088 lies 51 million light years away. My RBG photo includes about 5 hours of imaging per channel with my 14-inch Planewave reflector and FLI 16803 CCD camera.

Mircea Pteancu: Observer from Romania

Mircea Pteancu of Arad, Romania

affiliated to Hungarian Astronomical Assoc., Romanian Society for Cultural Astronomy, 

“Galaxies” Astronomy Club, moderator on forum.

At my observation site, the weather this Spring has been terrible for deep-sky observing, with  the sky being almost permanently cloudy and or hazy. 

I had only one opportunity to observe galaxy NGC 4088, being on March 21. The telescope used was my “SkyWatcher Classic 250P” Dobsonian reflector at 171x in a 28 arc minute field.  My sketch was obtained with a 7mm UWA eyepiece. The observation site used provides a Bortle5/6 sky in good conditions. However, on the evening of the observation, haze and thin clouds were present in the atmosphere and I think it affected the magnitude limit of my telescope by one class.

A summary of my observation session can be viewed here:

The galaxy NGC 4088 is located in the same field with the variable star HZ UMa. The object have in my telescope has a hazy aspect, pretty homogeneous with luminosity being over the entire surface. I detected only a slight increase of brightness toward its center. NGC 4088 has an oval shape, the long axis being oriented toward PA 30° to 40º and equal in length to the distance between stars marked as “a”   and “b”. 

I estimated the short axis of the galaxy to be about 60% to 70 % of the long one. 

In the same 28’ field with NGC 4088, there is a much smaller and dimmer galaxy, NGC 4085.

Located to the South of NGC 4088, and really close to the variable star HZ UMa, NGC 4085 is much more difficult to see. I could only see with averted vision. Except for its existence and approximate location, I have been unable to derive a size and shape for NGC 4085.

The brightest stars in the visual field were the stars HZ UMa and the nearby star HD 105072 of magnitude 8.64.

The dimmest star in the field was the one marked “b” on the drawing, of magnitude 12.29.

I used for this report…data according to Simbad through Aladin Lite. When preparing this report, the star HD 105072 awakened my “hunter attention” because I learned through interrogation of CDS portal this is a “Double or Multiple Star”. The site “” confirmed this. The separation would be within the proven capability of my telescope but the companion being of magnitude 13.06, not much hope. 

While still in Aladin Lite I did not find informations about an object of stellar aspect, located to the west of the visual field, between two stars of 10.05 and 11.37 magnitudes, respectively. It is probably a not catalogued star. Who knows? Very fine field!

Ionel and Armand, two members of our club who attended the observation, saw NGC 4088 also.

Armand, who is a very keen visual observer (and much younger) saw NGC 4085 much easier than myself. However, this was not reason for sadness to me, because he is my pupil. I am proud that I have contributed to him becoming a very good visual observer!

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