Photography & Science
Using the 6-inch Celestron Origin Astrograph For Science Education
Less than one month after my Origin's first light, I began capturing star fields for educational purposes - my education! For example, this image captured the beautiful Double Cluster in Perseus, NGC 869 and NGC 884. It's just one photograph like thousands of others; no big deal. What is a big deal is all of the astronomy scattered throughout this 1.27" x 0.85" field of view just waiting to be explored.
After surviving a stroke, my new Celestron Origin Astrograph is playing a significant role in my rehabilitation. It was important that I learn to read again, comprehend what I was reading, and re-learn everything that I no longer knew about astronomy, physics, mathematics, and science in general. It's been a hard journey but I am proud to say that I finally, after more than a decade, read a book cover to cover - The Perfect Machine: Building the Palomar Telescope, Ronald Florence, HarperPerennial, New York, 1994. I am currently working my way through an advanced university level textbook filled with mathematics from simple geometry to calculus - Fundamental Astronomy, 6th Edition, Hannu Karttunen, Pekka Kröger, Heikki Oja, Mark Poutanen, and Karl Johan Donner, Editors, Springer-Verlag, Berlin, 2017.
So, let's analyze this photograph using all of the knowledge I have gained over the last year and a half, making good use of astronomy books, magazines, online surveys, and apps.
Logbook
Date & Time: August 12, 2024, 10:04 p.m.
Location: Kempt Shore, Nova Scotia, Canada, 45°N
Conditions: Clear
Moon: First quarter (54%)
Moonset: 11:38 p.m.
Technical: 10-sec exposures, 30-min integration, line power, no filter, no post-processing
Celestron Origin Astrograph Image
One of the most obvious features of this 1.27° x 0.85° field of view photograph is the presence of several red supergiant stars. I have labeled seven of them. These huge stars have variable visual magnitudes, some periodic and others without regular periods. Let's have a look at their visual magnitudes, spectral types, and effective temperatures (from Ref.1). All seven are candidate members of the Perseus OB1 Association.
AD Per (HD 14270, BD+56 547), V 7.8, M2.5 Iab, Teff ~ 3250, Per OB1 membership candidate
FZ Per (HD 14330, BD+56 551), V 7.9, M1 Iab, Teff ~ 3500, Per OB1 membership candidate
RS Per (HD 14488, BD+56 583), V 8.50, M4.5 Iab, Teff ~ 2950, Per OB1 membership candidate
SU Per (HD 14469, BD+55 597), V 7.55, M3.5 Iab, Teff ~ 3100, Per OB1 membership candidate
V403 Per (HD 14580, BD+56 597), V 8.4, M0 Iabvar, Teff ~ 3800, Per OB1 membership candidate
V439 Per (BD+56 595), V 8.18, M0 Iab, Teff ~ 3800, Per OB1 membership candidate
V441 Per (HD 14826, BD+65 609), V 8.24, M2 Iab, Teff ~ 3300, Per OB1 membership candidate
Reference 2 lists 13 M-type supergiants, the seven above plus the six below. Data is from SIMBAD, AAVSO, SkySafari 7 Pro, and Refs. 1 & 2.
HD 13136 (KK Per, BD+55 529), V 7.49-7.99, P 345 d, M2 Iab-Ib, Teff ~ 3220°C
BD+56 512 (BU Per), V 8.2-10.1, P 432 d, M4 Ib, Teff ~ 2930°C
HD 14142 (T Per, BD+58 439), V 8.3-9.0, P 2430 d, M2 Iab, Teff ~ 3100°C
HD 14404 (PR Per, BD+57 550), V 7.7-8.2, P None, M1 Iab-Ib, Teff ~ 3220°C
HD 14528 (S Per, BD+57 552), V 7.9-12.8, P 822 d, M4.5-7Iae, Teff ~ 2930°C
HD 236979 (YZ Per, BD+56 673, V 7.66-8.73, P 378 d, M1 Iab, Teff ~ 3220°C
References
1. "Galactic OB Associations in the Northern Milky Way Galaxy. I. Longitudes 55° to 150°," C.D. Garmany and R.E. Stencel, Astron. Astrophys. Suppl. Ser. 94, 211-244 (1992).
2. "The M-type supergiant members of the Double Cluster in Perseus," W.P. Bidelman, Astrophysical Journal, 105, 492 (1947).
Celestron Origin Astrograph Image
There are many types of variable stars in this field of view. I have labelled a small sample of seven. All of these variables are members of the Perseus OB1 Association (Ref. 1).
V359 Per (HD 14250, BD+56 545), V 8.96, B1 III, pulsating variable, Per OB1 member
V360 Per (BD+56 589), V 9.46, B1 III, pulsating variable, Per OB1 member
V424 Per (HD 14422, BD+56 565), V 8.99, B0 IVpe, Be star, Per OB1 member
V520 Per, (HD 14134, BD+56 522), V 6.55, B3 Ia, blue supergiant irregular variable, Per OB1 member
V595 Per, (BD+56 575), V 9.08, B0.5 IV, β Cephei variable, Per OB1 member
V621 Per (BD+56 576), V 9.38, B2 III, Algol eclipsing binary, Per OB1 member
V757 Per (HD 14053, BD+56 498), V 8.43, B0.5 III, β Cephei variable, Per OB1 member
A Look at Distances
Per OB1 Association
We can estimate the distance to the Perseus OB1 Association using the distance modulus of 11.8 from Reference 1 and Equation 4.12 from Reference 3;
m-M = 5log (r/10 pc),
where m-M is the distance modulus, 10 parsecs is the reference distance, and r is the distance to the object of interest in parsecs. Note that 1 parsec (pc) = 3.26 light-years (lys). Extinction by the interstellar medium due to scattering and absorption is included in the 11.8 modulus. Solving for r we find the distance to Perseus OB1 to be approximately 2300 pc, or 7,500 lys.
This 11.8 distance modulus includes extinction. R.L. Wildey (Ref. 4) states, "The extremely patchy interstellar absorption in this region makes photometric study difficult." Furthermore, W.P. Bidelman (Ref. 5) discusses a nearby absorbing lane thusly, "The absorption is seen to extend quite uniformly across the field, from slightly to the south of the double cluster; and even at a distance of only a few degrees from the cluster the absorption is very heavy, for there are numerous places where no stars show at all."
References
3. Fundamental Astronomy, 6th Edition, Hannu Karttunen, Pekka Kröger, Heikki Oja, Markku Poutanen, and Karl Johan Donner, Editors, Springer-Verlag, Berlin, 2017, p. 96.
4. "The stellar content of h and χ Persei—Cluster and association," Robert L. Wildey, Astrophysical Journal Supplement, 8, 439-496 (1964).
5. " A spectroscopic study of the region of the double cluster in Perseus," William P. Bidelman, Astrophysical Journal, 98, 61-81 (1943).
21 Stars in the χ Persei (NGC 884) Nucleus
Catalogue Identifiers and star types
All 21 stars have identification numbers originally assigned by A. Van Maanen (Ref. 6) and studied by R.E. Schild (Ref. 7). They are listed below with GAIA and other useful catalogue numbers as well as star type.
- 2088, GAIA DR3 458453334698292096, BD+56 563, TYC 3694-2081-1, V506 Per (Be star)
- 2114, GAIA DR3 458453162899636096, (Pulsating variable)
- 2139, GAIA DR3 458454640368346624, (Variable star)
- 2165, GAIA DR3 458454880886508032, BD+56 566, TYC 3694-1792-1, V507 Per (Be star)
- 2185, GAIA DR3 458406124415716224 (Variable star)
- 2196, GAIA DR3 458454777807293824 (Star)
- 2227, GAIA DR3 458454606008605312, HD 14443, BD+56 570, TYC 3694-1680-1 (Variable star)
- 2229, GAIA DR3 458454777808585216 (Star)
- 2232, GAIA DR3 458454571648871680 (Eclipsing binary)
- 2235, GAIA DR3 458454606008607232, BD+56 571, TYC 3694-2433-1 (Pulsating variable)
- 2242, GAIA DR3 458454709081938048 (Be star)
- 2246, GAIA DR3 458454606008606336, BD+56 572, V619 Per (β Cep variable)
- 2151, GAIA DR3 458454601700570752 (Eclipsing binary)
- 2255, GAIA DR3 458454709087817344 (Star)
- 2262*, GAIA DR3 458455185816111872, TYC 3694-1433-1 (Emission-line star)
- 2284, GAIA DR3 458406090055982336, BD+56 573, TYC 3694-1707-1 (Be star)
- 2296, GAIA DR3 458407601884442496, BD+56 574, TYC 3694-2191-1 (Variable star)
- 2299, GAIA DR3 458407670603899648, BD+56 575, TYC 3694-1255-1, V595 Per (β Cep variable)
- 2301, GAIA DR3 458407601884424576, V620 Per (Eclipsing binary)
- 2311, GAIA DR3 458407601884432384, BD+56 576, TYC 3694-1387-1, V621 Per (Eclipsing binary)
- 2371, GAIA DR3 458407533164943360, BD+56 578, TYC 3694-2229-1, V622 Per (Be star)
*Note that the Fig.1 finding chart in Ref. 7 has an error. Star 2264 should be 2262 to match the identification number in Table 1 of the same paper.
References
6. "The proper motions of 1418 stars in and near the clusters h and χ Pers.," A. Van Maanen, Rech. Astr. de l"Obs. d'Utecht, 5 , 1911.
7. "Spectral classification in h and χ Persei," Rudolf E. Schild, Astrophysical Journal 142, 979-982 (1965).