Introduction The Hidden Treasures list comprises 109 Deep Space Objects (DSO) compiled by the well-known astronomer Stephen James O’Meara visible form his home location in Hawaii. It includes objects not included in either the Messier or Caldwell catalogues. This new list was compiled to fill gaps in both the Messier and Caldwell lists. The Messier list was compiled as an aid to avoiding ‘embarrassing’ objects, which might be mistaken for comets with the poor quality telescopes available at the time. The Caldwell list was compiled by Patrick Moore to include objects he thought were aesthetically pleasing, visually challenging or of astrophysical interest. The Hidden Treasures list is aimed at including the ‘best and brightest’ objects not included by Messier or Moore in their catalogues. The list was compiled over the course of 10 years and underwent more than two dozen revisions during that time, but finally comprises – 109 objects; 38 Open Star Clusters, 35 Galaxies, 14 Planetary Nebulae, 8 Globular Star Clusters, 8 Bright Nebulae, 1 Dark Nebula, 1 Star with a large proper motion and 4 Asterisms. Each Hidden Treasure in the list is prefixed by the letter ‘H’. It is hoped the ‘H’ list will become as popular as those of Messier, Caldwell and the Herschel 400. It deserves to because it contains many of the ‘best and brightest’ DSOs neglected by both Messier and Moore. My astrophotography efforts began in 1975 but my ability to obtain acceptable images was hampered by the need for lots of equipment and materials to process film and make final prints and lack of time to adequately develop the skills required. That situation changed dramatically in 2004 when I purchased a Canon EOS 20D digital

single lens reflex camera. Relatively quickly, the resulting images began to meet the quality standards I had set for myself and I began a concerted program of deep-sky astrophotography. Three books provided some of my inspiration:

Atlas of Deep-Sky Splendors, Hans Vehrenberg, 1971. The Messier Album, John H. Mallas and Evered Kreimer, 1978. The Cambridge Deep-Sky Album, Jack Newton and Philip

Teece, 1983. Goals

Photograph all the Hidden Treasures visible from my location in Prescott Valley, Arizona - 6 objects were too far south to be photographed.

When possible display all the objects with identical image scale for size comparison

Show that quality images can be obtained from modest-sized high quality equipment

The Cameras

Canon EOS 20Da, 3504 x 2336 pixel CMOS, 8.2 Mpx Canon EOS 60Da, 5184 x 3456 pixel CMOS, 17.9 Mpx

The sizes of the imaging chips in the cameras are the identical APS format. As a result the 60Da has 1.48 times more pixels per inch than the 20Da. When images from the cameras are displayed at the same resolution on a computer screen, the images from the 60Da will be 1.48 times larger. Images obtained with the 60Da have been designated with an asterisk (*). The Optical Systems

Canon EF 180mm f3.5L Macro USM Canon EF 100-400mm f/4.5-5.6L IS USM set at 400mm f/5.6 Takahashi Sky 90 with 0.8X focal reducer/field flattener - 405mm

f/4.5

The Mounts

Vixen GPDX equatorial mount with SkySensor 2000 on JMI Wheeley Bars

Software Bisque Paramount MX equatorial mount on a permanent pier controlled by TheSkyX Pro and an Apple MacBook Pro laptop computer.

Focusing Initially focusing was done manually while observing a star through a Canon Angle Finder C at 2.5x magnification. The quality of focus was checked by examining a test image on the camera's LCD screen. Unfortunately image focus varied significantly, resulting in refocusing and second or even third images being acquired. Eventually a JMI Motofocus and a Bahtinov mask were added to the Sky 90 optical system. Focus was achieved by observing the Bahtinov diffraction pattern on the computer screen using Stack Labs' Nebulosity 3. This focusing method is vastly superior to the manual method and the need to repeat image acquisition was eliminated. Image Acquisition The basic image acquisition scheme was to obtain 5 dark-frames, then 30 light-frames and finally 5 more dark-frames, yielding an image set of 10 dark-frames and 30 light-frames for calibrating and stacking. Exposure duration of each frame was 1 minute at ISO 1600 (20Da) or ISO 3200 (60Da) with a 10-second delay between exposures and a 5-second delay from sequence initiation and the first exposure. No bias or flat frames were used. Images were saved as highest quality JPEG files on the cameras' memory cards. Image acquisition was controlled with a Canon Timer Remote Controller TC-80N3. Basic Image Processing The 30 light-frames were examined and any with bright satellite or airplane trails were discarded. DeepSkyStacker 3.3.2 was used to

calibrate and stack the good frames (usually 27 to 30) from each image set. The final raw stacked image file was saved as a 32-bit TIFF file. Image enhancement and optimization was performed with Adobe Photoshop CS2. First the image file Mode was changed to 16-bit. While examining the upper right corner of the image, Levels was used to adjust the RGB black point such that R=G=B at a value of 10-15.

Using Curves, the low intensity nebulosity was enhanced while not 'blowing out' bright zones or causing the black background to lighten significantly by setting Curves set points approximately as shown in the figure above. Any resulting vignetting in background sky intensity was 'neutralized' using techniques similar to those described in "Fixing Vignetting in Astrophotos", Sean Walker, Sky & Telescope, September 2001 and the book Photoshop Astronomy by R. Scott Ireland. Finally a modest Unsharp Mask (amount: 100%, radius: 1.0 pixel, threshold: 3 levels) was applied.

The image scale of the three optical systems was determined using Adobe Photoshop CS2 and Voyager 4 Dynamic Sky Simulator. Then the image scale of the images from the Canon EF 180mm and Canon EF 100-400mm optical systems were up-sampled to match that of the Takahashi Sky 90 optical system for images obtained with the Canon 20Da. Images obtained with the Canon 60Da are displayed with image scale unchanged at 1.48 times that of the 20Da. Images were then appropriately cropped and combined to make the album pages with all the objects at the same image scale for direct comparison. Final Thoughts The images in the album were acquired over a period of 5 years with continuous improvement in equipment, techniques and skills. I am well aware that a number of images could be significantly improved and better photographs will be acquired in the future. In addition, a number of the planetary nebula are essentially 'stellar' in appearance and require significantly greater focal length and image scale yielded by larger OTAs to show detail. But 'perfection' can often be the enemy of 'finishing' so those better images await the second edition of this album. Eventually I would like to obtain images of the 6 remaining most southerly Hidden Treasures by subscribing to the internet telescope rental service iTelescope and use the equipment available in Siding Springs, Australia.

Hidden Treasures

OC: open cluster PN: planetary nebula SG: spiral galaxy GC: globular cluster IG: irregular galaxy EG: elliptical galaxy BN: bright nebula SR: supernova remnant DN: dark nebula A Canon 180mm B Canon 100-400mm C Sky 90

H NGC/IC Type RA Dec Optics 1 189 OC 00h 39m 36s +61º 05' 42" C 2 225 OC 00h 43m 36s +61º 46' 00" C 3 281 BN 00h 52m 54s +56º 37' 30" C 4 288 GC 00h 52m 46s -26º 35' 51" C 5 404 SG 01h 09m 27s +35º 43' 06" C 6 584 SG 01h 31m 20s -06º 52' 02" C 7 659 OC 01h 44m 24s +60º 40' 12" C 8 772 SG 01h 59m 20s +19º 00' 27" C 9 908 SG 02h 23m 05s -21º 14' 00" C 10 1023 SG 02h 40m 24s +39º 03' 48" C 11 1232 SG 03h 09m 45s -20º 34' 45" C 12 1291 SG 03h 17m 18s -41º 06' 26" C 13 1316 SG 03h 22m 42s -37º 12' 00" C 14 Mel 20 OC 03h 24m 18s +49º 52' 00" A 15 1333 BN 03h 29m 18s +31º 25' 00" C 16 1360 PN 03h 33m 15s -25º 52' 16" C 17 1365 SG 03h 33m 37s -36º 08' 27" C 18 1399 EG 03h 38m 29s -35º 26' 59" C 19 1398 SG 03h 38m 52s -26º 20' 14" C 20 1404 EG 03h 38m 52s -35º 35' 34" C 21 Kemble 1 Asterism 03h 57m 24s +63º 04' 00" C 22 1501 PN 04h 06m 59s +60º 55' 17" C 23 1502 OC 04h 07m 49s +62º 19' 54" C 24 1535 PN 04h 14m 16s -12º 44' 20" C 25 1528 OC 04h 15m 19s +51º 12' 42" C 26 1545 OC 04h 20m 56s +50º 15' 19" C 27 1647 OC 04h 45m 42s +19º 07' 09" B 28 IC 418 PN 05h 27m 28s -12º 41' 48" C 29 Cr 69 OC 05h 35m 00s +09º 56' 00" C 30 1981 OC 05h 35m 12s -04º 26' 00" C 31 Cr 72 OC 05h 35m 24s -05º 55' 00" C 32 1977 BN 05h 35m 18s -04º 49' 15" C 33 1999 BN 05h 36m 25s -06º 42' 57" C 34 2024 BN 05h 41m 42s -01º 51' 24" C 35 2163 BN 06h 07m 50s +18º 39' 27" C 36 2169 OC 06h 08m 24s +13º 57' 53" C 37 2175 BN 06h 09m 39s +20º 29' 18" C 38 2264 OC 06h 40m 58s +09º 53' 44" C

H NGC/IC Type RA Dec Optics 39 2301 OC 06h 51m 45s +00º 27' 33" C 40 2353 OC 07h 14m 30s -10º 15' 57" C 41 2440 PN 07h 41m 55s -18º 12' 29" C 42 2451 Asterism 07h 45m 24s -37º 57' 00" C 43 2467 BN 07h 52m 26s -26º 26' 12" C 44 2547 OC 08h 10m 09s -49º 13' 30" 45 2539 OC 08h 10m 37s -12º 49' 14" C 46 2546 OC 08h 12m 24s -37º 37' 00" C 47 2683 SG 08h 52m 41s +33º 25' 12" C 48 2655 SG 08h 55m 38s +78º 13' 25" C 49 2841 SG 09h 22m 02s +50º 58' 35" C 50 IC 2488 OC 09h 27m 27s -56º 57' 24" 51 2903 SG 09h 32m 10s +21º 29' 57" C 52 3184 SG 10h 18m 17s +41º 25' 24" C 53 3228 OC 10h 21m 22s -51º 43' 42" 54 3293 OC 10h 35m 51s -58º 13' 48" 55 3344 SG 10h 43m 31s +24º 55' 22" C 56 3521 SG 11h 05m 49s -00º 02' 13" C 57 3621 SG 11h 18m 16s -32º 48' 40" C 58 3628 SG 11h 20m 17s +13º 35' 24" B 59 4214 IG 12h 15m 39s +36º 19' 39" C 60 4216 SG 12h 15m 54s +13º 08' 52" C 61 4361 PN 12h 24m 31s -18º 47' 03" C 62 Mel 111 OC 12h 25m 06s +26º 07' 00" A 63 4490 SG 12h 30m 36s +41º 38' 34" C 64 IC 3568 PN 12h 33m 07s +82º 33' 51" C 65 4526 SG 12h 34m 03s +07º 41' 56" C 66 4605 SG 12h 39m 59s +61º 36' 30" C 67 4656 SG 12h 43m 58s +32º 10' 11" C 68 4699 SG 12h 49m 02s -08º 39' 50" C 69 4725 SG 12h 50m 26s +25º 30' 00" C 70 5102 SG 13h 21m 57s -36º 37' 54" C 71 5281 OC 13h 46m 37s -62º 54' 34" 72 5363 SG 13h 56m 07s +05º 15' 14" C 73 5662 OC 14h 35m 31s -56º 39' 46" 74 5746 SG 14h 44m 56s +01º 57' 22" C 75 5866 SG 15h 06m 29s +55º 45' 49" C 76 5897 GC 15h 17m 24s -21º 00' 35" C 77 5986 GC 15h 46m 04s -37º 47' 08" C 78 6210 PN 16h 44m 30s +23º 48' 02" C 79 6242 OC 16h 55m 31s -39º 28' 01" C 80 6281 OC 17h 04m 47s -37º 53' 16" C 81 6369 PN 17h 29m 20s -23º 45' 33" C 82 6400 OC 17h 40m 12s -36º 57' 42" C 83 IC 4665 OC 17h 46m 12s +05º 43' 00" C 84 6445 PN 17h 49m 15s -20º 00' 32" C

H NGC/IC Type RA Dec Optics 85 6503 SG 17h 49m 28s +70º 08' 37" C 86 6441 GC 17h 50m 13s -37º 03' 02" C 87 Barnard's Star 17h 57m 48s +04º 40' 06" C 88 6520 OC 18h 03m 25s -27º 53' 28" C 89 6544 GC 18h 07m 21s -24º 59' 49" B 90 6572 PN 18h 12m 06s +06º 51' 15" C 91 6624 GC 18h 23m 40s -30º 21' 38" C 92 6633 OC 18h 27m 15s +06º 30' 30" C 93 IC 4756 OC 18h 38m 54s +05º 26' 00" C 94 6709 OC 18h 51m 30s +10º 20' 00" C 95 6712 GC 18h 53m 04s -08º 42' 20" C 96 6723 GC 18h 59m 33s -36º 37' 52" C 97 Cr 399 Asterism 19h 26m 12s +20º 06' 00" A 98 6819 OC 19h 41m 18s +40º 11' 00" C 99 6818 PN 19h 43m 58s -14º 09' 09" C

100 6866 OC 20h 03m 55s +44º 09' 33" C 101 6940 OC 20h 34m 32s +28º 16' 49" C 102 N Coalsack DN 20h 40m 00s +41º 00' 00" B 103 7008 PN 21h 00m 33s +54º 32' 38" C 104 7027 PN 21h 07m 02s +42º 14' 12" C 105 Tr 37 OC 21h 39m 00s +57º 30' 00" C 106 7380 OC 22h 47m 21s +58º 07' 54" C 107 O'Meara1 Asterism 23h 40m 42s +07º 57' 00" C 108 7789 OC 23h 57m 29s +56º 42' 52" C 109 7793 SG 23h 57m 49s -32º 35' 30" C