When to photograph M 75
M 75 is a globular cluster in Sagittarius, 4′ across at magnitude 8.3. Also listed as NGC 6864.
When to photograph it
From 45° N it never climbs above 30°. It peaks at 23° when it crosses the meridian, low enough that haze and light pollution soften it. It is possible with a clear southern horizon, but hard.
From 35° S the best months are June to August, with up to 9.0 hours of astronomical darkness above 30° in July. It reaches 77° at its highest.
Framing
At 4′ it is small. Even 4000 mm of focal length leaves it filling less than a third of an APS-C frame, so it suits long focal lengths, small pixels and good seeing.
Filters and the moon
Clusters are broadband targets, but bright ones tolerate some moonlight and light pollution. Short subs keep the brightest stars from clipping. The dark sky calendar shows which nights this month are moon-free where you are.
Plan it for tonight
Dates and times depend on your exact location. The imaging planner shows M 75's altitude through tonight, its transit time and its distance from the moon. For sub length, use the exposure calculator.
Nearby targets
- NGC 6822 Barnard's Galaxy 8.7° away
- M 55 10.8° away
- M 72 14.7° away
- M 73 15.6° away
- NGC 7009 Saturn Nebula 17.4° away
- M 54 18.1° away
Gear that suits M 75
M 75 is only 3.6′ across, so it stays small in any amateur telescope. The longest focal length gives it the most pixels.
- Celestron C8 OTA 2032 mm f/10: fills 14% of an APS-C frame's short side View at High Point Scientific
Retailer links are affiliate links. If you buy through one, the site may earn a commission at no extra cost to you. Details