It never ceases to surprise me how few observers have a set of 2-inch high quality UHC, OIII and H-Beta filters and instead more people seem to have a couple UHC and OIII 1.25” filters which they seldom use. They likely migrated to 2-inch low power eyepieces and their 1.25” lowest powers yield exit pupils too small to get the most effective use of those filters. Additionally, the wider fields afforded by 2-inch filters are what really make these tools shine. The most useful exit pupils are between 4mm and 7mm in a 2-inch format. Still, one must enjoy the subtlety of observing ethereal targets which are scarcely there even under excellent skies.
The initial observations were made with 7×50 Vixen Geoma Binoculars, 22×100 Antares binoculars (which work at something like 22×85) and my favourite scope, the Borg 125SD containing Pentax lenses with a 3.5-degree true field with my 40mm Pentax XW and 30mm Widescan III. Additionally I had Orion OIII and H-Beta Filters plus a Baader UHC-S.
More recently I have moved to several wide field scopes, a Takahashi 100DC for it’s superb optics, true high power planetary abilities and an slightly wider field than the 125SD. A Takahashi FS60 with a 7.5-degree true field and Borg 50mm F5 Acho which has been modified by Shane Ludtke to give me over 10-degree fields. The Pentax 40mm XW remains a superb though heavy eyepiece so I end to favour a recently acquired 32mm Masuyama with a 44mm field stop (Marked 84-degree but actual field is ~78-
Most of these objects can be viewed in those portable 60mm to 100mm f5 to f7 refractors using a very low power 2-inch eyepiece. These scopes are also excellent for taking on a trip to a dark site packed in a suitcase. Consider picking up some 2 inch filters for this scope.
NGC 206 is a Star Cloud within dark lanes of M31 best seen in wide fields with M31 dust lanes to SW; use M32 and mag. 7 star to locate. Well seen in 5&6 inch telescopes.
Collinder 463 is an Open Cluster in Cassiopeia located at the edge of the Milky Way in the four corners region of Cassiopeia, Cephus, Camelopardalis and Ursa Minor.
The “Crescent Cluster” appears as 4 dozen stars scattered in a crescent
Size: 57 arc minutes (Almost 1 degree)
Stock 2 in Cassiopeia is an Open Cluster located at 02 16 +59 33
Common Name: Mushroom Cluster
How to find: Locate the Double Cluster and follow the meandering star chain north about 2-degrees to Stock 2.
Observation: Try to see the Double Cluster and Stock 2 in the same wide field.
IC 1805 & 1848 in Cassiopeia is a complex of Emission Nebulae and clusters located at 02 34 +61 29
Size: 4.5 degrees
Magnitude: Not Applicable
Common Name: Heart and Soul Nebulae
Observation: A large complex of nebulae and star clusters; use filter; IC 1795 is brightest part of IC 1805. Well seen in 50mm and 60mm telescopes with 2-inch eyepieces and 2-inch UHC filters.
Cosmic Question Mark “?” is an Asterism located in Cetus at 02 37 +06 56
Observation: Best seen in Autumn and early Winter when the asterism is vertical and it looks exactly like a large question mark and is best seen in binoculars
Melotte 20 is a huge Open Cluster in Perseus loathed at 03 25 +49 54
Common Name: Perseus OB3 Association
Observations: Surrounds Mirfak, the brightest star in Perseus. A large cluster for small binoculars; look for a miniature “Draco” asterism, including 4 stars denoting the head. Visible from the darkest skies naked eye as a chandelier in the middle of Perseus.
Kemble’s Cascade is an Asterism located in Camelopardalis located at 03 59 +63 06
Observations: A colourful chain of 20+ stars terminates at NGC 1502; named by Walter Scott Houston in honour of Father Lucian Kemble (1922–1999). Best seen in small scopes and binoculars.
Taurus Molecular Cloud in Taurus is a Giant Molecular Cloud (GMC) located 4h–5h +16–31
Observation: M45, the Pleiades, is passing through dust and gas in space. While Messier never glimpsed the nebula, images of the cluster show this blue gauzy glow. While the Merope Nebula and some of the glow is often observed many other components of this giant space cloud can be viewed with small refractors. Try a very broadband UHC filter. Objects can be identified as NGC 1435, IC 353/349/1995; as well as many dark nebulae appearing as “haze” over a dim background star field. However, this should include the Taurus Dark Nebula Complex to the north in an area between Perseus, Taurus and Auriga which is rich in large dark lanes easily seen over starclouds.
NGC 1499 in Perseus is an Emission Nebula located at 04 02 +36 39
Size: 145×40 arc minutes
When people ask where to start with H-Beta targets I send them to California. Located midway between Zeta Per and Adid Australis, just off Menkib the California Nebula is easily seen under most descent dark skies with the H-beta filter and I’ve viewed it from excellent skies using only 7×50 binoculars and no filters. Use magnification of 15× to 30× to detect the wave detail and to train your eye for fainter objects. For best views observe this target as it passes through the Zenith.
Sh2-245 Is an emission Nebula located in Taurus at 04 03 +03 06
Observation: Known as the Eridanus Arc for its greater extent projecting into this constellation to the SE. Use an H-beta filter; look for the brightest section 3° S of n Tau.
In the April 2009 edition of Sky & Telescope magazine Dennis di Cicco and Sean Walker presented “Imaging the Orion-Eridanus Superbubble”. I was never so excited about a magazine article since their images revealed many “new” nebulae apparently as bright as Barnard’s Loop which my new 5-inch refractor was easily showing. So armed with the H-Beta filter I tracked down several of these targets with the “Eridanus Arc” being among my favourites as few observers had seen this visually.
NGC 1647 is an Open Cluster in Taurus located at 04 47 +19 10
Size:40 arc minutes
Observation: This is a large binocular cluster, 5° northeast of the Hyades. It is a bright, often overlooked cluster where a telescope reveals many “double” stars. It may be glimpsed without aid in a dark sky.
NGC 1746 is an Open Cluster in Taurus located at 05 05 +23 50
Size: 42 arc minutes
Observation: NGC 1750 on the SW and NGC 1758 on the SE are superimposed over the bottom half of this cluster. 15× binoculars show a nice cluster embedded in a chain of meandering stars
Collinder 65 is an Open Cluster in Taurus located at 05 27 +16 43
Observation: Appears as a Giant Mushroom binocular cluster, beautiful, but often not marked on charts; large mushroom-shaped arrow.
Sh2-264, the “Angelfish Nebula” is a huge Emission Nebula in Orion located at 05 36 +09 56
Observation: The Angelfish Nebula is visible using the H-Beta filter in the vicinity of Lambda Orionis and the scattering of stars associated with Collinder 69, an open cluster. The nebula is bright enough to piece together using larger telescopes and some have even seen it using the filter held up to the eye alone.
Collinder 70 is an OB1 Association Open CLuster in Orion located at 05 36 –01 06
Observation: 3-D view of Orion belt stars over distant field; look for S-shaped star chain W of ε Orionis.
Orion GMC is a Giant Molecular Cloud in Orion centred on 05 42 –02 24
Size: 1°×2° bright section
Observation: Use low-power binoculars and filters; look for wave and gap SW of ε Orionis.
Image by Andrea Girones illustrating the waves and gap south of Orion’s Belt
IC 2118 is known as the “Witch Head Nebula” which a Reflection Nebula in Eridanus at 05 08 –07 12
Observations: Use low-power, wide-field binoculars or telescopes on best nights, keep Rigel out of the field.
Simeis 147 (Sh2-240) is a SuperNova Remnant in Taurus centred on 05 41 +28 06
Observation: If you thought any of the previous objects were challenging…well… they were on the learning curve. Wait for it to culminate at the Zenith and use filters, a 5 inch or larger refractor or an 8-inch or larger reflector. Look for “Skates Egg” knot, 10′ E of mag. 8 star SAO 77397.
Collinder 89 is an Open Cluster in Gemini at 06 19 +23 38
Size: 60 arc minutes (1-degree)
Observation: large, loose cluster
Collinder 132 is an Open Cluster in Canis Major centred on 07 16 –30 42
Size: 80 ac minutes
Observation: A large cluster and a sprinkling of colourful stars visible even during full Moon. Likely what Aristotle wrote about as appearing comet-like vs. the often cited M41 to the north.